Changes

These files have = Standard MIDI File (SMF) Format = The <B>Standard MIDI File</B> (SMF) is a file format used to store MIDI data (plus someother kinds of data typically needed by a sequencer. This format stores the standard MIDI messages (ie, status bytes with appropriate data bytes)plus a time-stamp for each message (ie, a series of bytes that represent how many clock pulsesto wait before "playing" the event). The format also allows saving information about tempo,time and key signatures, the names of tracks and patterns, and other information typicallyneeded by a sequencer. One SMF can store information for numerous patterns and tracks so that anysequencer can preserve these structures when loading the file. <B><FONT COLOR=RED>NOTE:</FONT></B> A <B>track</B> usually is analogous to one musical part,such as a Trumpet part. A <B>pattern</B> would be analogous to all of the musical parts (ie,Trumpet, Drums, Piano, etc) for one song. The format was designed to be generic so that the most important data can be read by allsequencers. Think of a MIDI file as a good deal musical version of an ASCII text file (exceptthat the Menu MIDI file contains binary data), and the various sequencer programs as texteditorsall capable of reading that file. But, unlike ASCII, MIDI file format saves data in <B>chunks</B>(ie, groups of bytes preceded by an ID and size) which can be parsed, loaded, skipped, etc.Therefore, SMF format is flexible enough for a particular sequencer to storeits own proprietary, "extra" data in such a way that another sequencer won't be confused whenloading the file and can safely ignore this extra stuff that it doesn't need.For example, maybe a sequencer wants to save a "flag byte"that indicates whether the user has turned on an audible metronome click. The sequencer can savethis flag byte in such a way that another sequencer can skip this byte withouthaving to understand what that byte is for. In the future, the SMF format can also beextended to include new "official" chunks that all sequencer programs may elect to load and use.This can be done without making old data files obsolete, nor making old sequencers no longerable to load the new files. So, the format is designed to beextensible in a backwardly compatible way. Of course, SMF files may be used by other MIDI software than just sequencers.Since SMF files can store any and all types of MIDI messages, including System Exclusivemessages, they may be used to store/load data by all kinds of MIDI software, such as a PatchEditor that wants to save some System Exclusive messages it received from a MIDI module. (The"timestamp" for each message may be irrelevant to such a Patch Editor.But it's easilyignored for programs that don't really need it). In conclusion, any software that saves or loads MIDI data should use SMF format for its datafiles. ===Header=Chunks =={| class=Data is always saved within a <B>chunk</B>. There can be many chunks inside of a MIDI file. Each chunk can be a different size (and likely will be). A chunk's size is how many (8-bit)bytes are contained in the chunk. The data bytes in a chunk are typically related in some way. For example, all of the bytes in one chunk may be for one particular sequencer track. The bytes for another sequencer track may be put ina different chunk. So, a chunk is simply a group of related bytes. Each chunk must begin with a 4 character (ie, 4 ascii bytes) <B>ID</B> which tells what "wikitabletype"! Typeof chunk this is. The next 4 bytes must form a 32-bit length (ie, size) of the chunk. <U>All chunks must begin with these two fields</U> (ie, 8 bytes), which are referred to as the<B>chunk header</B>. Here's what a chunk's header looks like if you defined it in C:<c>struct CHUNK_HEADER{ char ID[4]; unsigned long Length; };</c><B><FONT COLOR=RED>NOTE:</FONT></B> The <B>Length</B> does not include the 8 byte chunk! Sizeheader. It simply tells you how many bytes of data are in the chunk <U>following this header</U>.! Value! DescriptionAnd here's an example chunk header (with bytes expressed in hex) if you examined it with a hex editor:|-| UInt16 4D 54 68 64 00 00 00 06| 2| Pad_CountNote that the first 4 bytes make up the ascii ID of <B>MThd</B> (ie, the first four| Always bytes are the ascii values for 'M', 'T', 'h', and '16d'). The next 4 bytes tell us that there shouldbe 6 more data bytes in the chunk (and after that we should find the next chunk header or the endof the file). === MThd Chunk === The MThd header has an ID of <B>MThd</B>, and a Length of <B>6</B>. Let's examine the 6 data bytes (which follow the MThd header) in an MThd chunk. The first two data bytes tell the <B>Format</B> (which I prefer to call "type").There are actually 3 different types (ie, formats) of MIDI files. A type of 0 means that the filecontains one single track containing midi data on possibly all 16 midi channels. If your sequencersorts/stores all of its midi data in one single block of memory with the data in the order that it's"played", then it should read/write this type. A type of 1 means that the file contains one ormore simultaneous (ie, all start from an assumed time of 0) tracks, perhaps each on a single midichannel. Together, all of these tracks are considered one sequence or pattern. If yoursequencer separates its midi data (i.e. tracks) into different blocks of memory but plays them back|simultaneously (ie, as one "pattern"), it will read/write this type. A type of 2 means that thefile contains one or more sequentially independant single-track patterns. If your sequencerseparates its midi data into different blocks of memory, but plays only one block at a time (ie,| UInt16[Pad_Count]each block is considered a different "excerpt" or "song"), then it will read/write this type. The next 2 bytes tell how many tracks are stored in the file, <B>NumTracks</B>. Of course,| for format type 0, this is always 1. For the other 2 * Pad_counttypes, there can be numerous tracks. The last two bytes indicate how many Pulses (i.e. clocks) Per Quarter Note (abbreviated as PPQN) resolution the time-stamps are based upon, <B>Division</B>. For example, if your sequencer has 96 ppqn, this field would be (in hex):  00 60 <B><FONT COLOR=RED>NOTE:</FONT></B> The 4 bytes that make up the <B>Length</B> are stored in (Motorola) "Big Endian" byte order, not (Intel) "Little Endian" reverse byte order. (ie, The 06 is the fourth byte insteadof the first of the four). In fact, all MIDI files begin with the above <B>MThd header</B> (and that's how you know that it'sa MIDI file). | PaddingsAlternately, if the first byte of Division is negative, then this represents the division| of a second that the time-stamps are based upon. The padding value leads first byte will be -24, -25, -29, or -30,corresponding to start the 4 SMPTE standards representing frames per second. The second byte (apositive number) is the resolution within a frame (ie, subframe). Typical values may be 4 (MIDITime Code), 8, 10, 80 (SMPTE bit resolution), or 100. You can specify millisecond-based timing by the data bytes of string offsets-25 and 40 subframes. Here's what an MThd chunk looks like if you defined it in C: <c>struct MTHD_CHUNK{ /* Here's the 8 byte header that all chunks must have */Can char ID[4]; /* This will be 'M','T','0x00h','d' ignore those */ unsigned long Length; /* This will be 6 */  /* Here are the 6 bytes */ unsigned short Format; unsigned short NumTracks; unsigned short Division;};</c> And here's an example of a complete MThd chunk (with header) if you examined it in a hex editor:<pre>4D 54 68 64 MThd ID00 00 00 06 Length of the MThd chunk is always 6.00 01 The Format type is 1.00 02 There are 2 MTrk chunks in this file.E7 28 Each increment of delta-time represents a millisecond.</pre> === MTrk Chunk ===After the MThd chunk, you should find an <B>MTrk chunk<br/B>, as this is the only otherFirst currently defined chunk. (If you find some other chunk ID, it must be proprietary to some otherprogram, so skip it by ignoring the following data bytes indicated by the chunk'sLength). An MTrk chunk contains all of the midi data (with timing bytes), plus optional non-midi datafor <U>one is usually track</U>. Obviously, you should encounter as many MTrk chunks in the file as theMThd chunk's NumTracks field indicated. The MTrk header begins with the ID of <b>MTrk</B>, followed by the Length (ie, number of data bytes for this track). The Length will likely be different for each track. (After all, a track containing the violin part for a Bach concerto will likely contain more data than a track containing a simple 2 bar drum beat). Here's what an MTrk chunk looks like if you defined it in C:<c>struct MTRK_CHUNK{ /* Here's the 8 byte header that all chunks must have */ char ID[4]; /* This will be 'M','T','0x36r','k'*/ unsigned long Length; /* This will be the actual size of Data[] */  /* Here are the data bytes */ unsigned char Data[]; /* Its actual size is Data[Length] */|};</c>  ===String Offsets= Variable Quantities ===={| class=Think of a track in the MIDI file in the same way that you normally think of a track in asequencer. A sequencer track contains a series of <B>events</B>. For example, the firstevent in the track may be to sound a middle C note. The second event may be to sound theE above middle C. These two events may both happen at the same time. The third event maybe to release the middle C note. This event may happen a few musical beats after the firsttwo events (ie, the middle C note is held down for a few musical beats). Each event has a"time" when it must occur, and the events are arranged within a "chunk" of memory in the orderthat they occur. In a MIDI file, an event's "time" precedes the data bytes that make up that event itself. Inother words, the bytes that make up the event's time-stamp come first. A given event'stime-stamp is referenced from the previous event. For example, if the first event occurs 4 clocksafter the start of play, then its "wikitabledelta-time"is 04. If the next event occurs simultaneously withthat first event, its time is 00. So, a delta-time is the duration (in clocks) between an eventand the preceding event. <B><FONT COLOR=RED>NOTE:</FONT></B> Since all tracks start with an assumed time of 0, the firstevent's delta-time is referenced from 0. A delta-time is stored as a series of bytes which is called a <B>variable lengthquantity</B>. Only the first 7 bits of each byte is significant (right-justified; sort of like anASCII byte). So, if you have a 32-bit delta-time, you have to unpack it into a series of 7-bit! Typebytes (ie, as if you were going to transmit it over midi in a SYSEX message). Of course, you! Sizewill have a variable number of bytes depending upon your delta-time. To indicate which is the! Valuelast byte of the series, you leave bit #7 clear. In all of the preceding bytes, you set bit #7. So,! Descriptionif a delta-time is between 0-127, it can be represented as one byte. The largest delta-time|allowed is 0FFFFFFF, which translates to 4 bytes variable length. Here are examples ofdelta-times as 32-bit values, and the variable length quantities that they translate to: <pre> NUMBER VARIABLE QUANTITY00000000 0000000040 400000007F 7F00000080 81 0000002000 C0 0000003FFF FF 7F00004000 81 80 0000100000 C0 80 00001FFFFF FF FF 7F00200000 81 80 80 0008000000 C0 80 80 000FFFFFFF FF FF FF 7F</pre>| UInt16| 2Here are some C routines to read and write variable length quantities such as delta-times. With| Offset_Count<B>WriteVarLen()</B>, you pass a 32-bit value (ie, unsigned long) and it spits out the correct| Number series of bytes to a file. <B>ReadVarLen()</B> reads a series of offsets before strings startbytes from a file until it|reaches the last byte of a variable length quantity, and returns a 32-bit value. <c>void WriteVarLen(register unsigned long value){ register unsigned long buffer; buffer = value & 0x7F;  while ( (value >>= 7) ) { buffer <<= 8; buffer | UInt16[Offset_Count]= ((value & 0x7F) | 0x80); }  while (TRUE) { putc(buffer,outfile); if (buffer & 0x80) buffer >>= 8; else break; }} unsigned long ReadVarLen(){ register unsigned long value; register unsigned char c;  if ( (value = getc(infile)) & 0x80 ) { value &= 0x7F; do { value = (value << 7) + ((c = getc(infile)) & 0x7F); } while (c & 0x80); }  return(value);}| 2 * Offset_count</c>| Offsets| <B><FONT COLOR=RED>NOTE:</FONT></B> The offset concept of variable length quantities (ie, breaking up alarge value into a series of bytes) is used with other fields in a MIDI file besides delta-times,as you'll see later. For those not writing in C, you may benefit from a psuedo-code explanation ofthe above routines. In pseudo-code, ReadVarLen() is: <OL><LI>Initialize the variable which will hold the value points . Set it to 0. We'llcall this variable 'result'.</LI><LI>Read the next byte of the Variable Length quantity from the MIDI file.</LI><LI>Shift all of the bits in 'result' 7 places to start the left. (ie, Multiply 'result' by 128).</LI><LI>Logically OR 'result' with the byte that was read in, but first mask off bit #7of the byte. (ie, AND the byte with hexadecimal 7F before you OR with'result'. But make sure you save the original value of the byte for the testin the next step).</LI><LI>Test if bit #7 of the byte is set. (ie, Is the byte AND hexadecimal80 equal to hexadecimal 80)? If so, loop back to step #2. Otherwise,you're done, and 'result' now has the appropriate value.</LI></OL> In pseudo code, WriteVarLen() could be: <OL><LI>Assume that you have a variable named 'result' whichcontains the value to write out as a Variable Length Quantity.</LI> <LI>Declare an array which can contain 4 numbers. We'll callthis variable 'array'. Initialize a stringvariable named 'count' to 0.</LI><LI>Is 'result' less than 128? If so, skip to step #8.</LI><LI>Take the value 'result' AND with hexadecimal 7F, and ORwith hexadecimal 80, and store it in 'count' element of 'array'.(ie, The first time through the loop, this gets stored in the firstelement of 'array'). NOTE: Don't alter the value of 'result' itself.Can <LI>Increment 'count' by 1.</LI><LI>Shift all bits in 'result' 7 places to the right. (This can be done by dividing by 128).</LI><LI>Loop back to step #3.</LI><LI>Take the value 'result' AND with hexadecimal 7F, and storeit in 'count' element of 'array'.</LI><LI>Increment 'count' by 1.</LI><LI>Write out the values stored in 'array'. Start with the lastelement stored above, and finish with the first element stored.(ie, Write them out in reverse order so that the first element of'0x00array'gets written to the MIDI file last). NOTE: The variable'count' ignore thosetells you how many total bytes to write. It also can beused as an index into the array (if you subtract one from it, andkeep writing out bytes until it is -1).</LI></OL>|}===String= Events in an MTrk ====Strings end with An MTrk can contain [http://www.borg.com/~jglatt/tech/midispec.htm MIDI events] and non-MIDI events (ie, events that contain data such astempo settings, track names, etc). The first (1 to 4) byte(s) in an MTrk will be the first event's delta-time as a variable lengthquantity. The next data byte is actually the first byte of that event itself. I'll refer to this asthe event's <B>Status</B>. For [http://www.borg.com/~jglatt/tech/midispec.htm MIDI events], this will be the actual MIDI Status byte(or the first midi data byte if running status). For example, if the byte is hex 90, then thisevent is a <B>Note-On</B> upon midi channel 0. If for example, the byte was hex 23, you'0x00d have torecall the previous event's status (ie, midi running status). Obviously, the first MIDI event inthe MTrk <U>must</U> have a status byte. After a midi status byte comes its 1 or 2 data bytes(depending upon the status - some MIDI messages only have 1 subsequent data byte). After thatyou'll find the next event's delta time (as a variable quantity), etc. [[FF8 ---- <CENTER><FONT COLOR=RED><B>SYSEX events</B></String_Encoding|Strings are encoded]].FONT><br/CENTER> SYSEX (system exclusive) events (status = F0) are a special case because a SYSEX event canbe any length. After the F0 status (which is always stored -- no running status here), you'll findyet another series of variable length bytes. Combine them with ReadVarLen() and you'll come upwith a 32-bit value that tells you how many more bytes follow which make up this SYSEX event.This length doesn'[Start t include the F0 status. For example, consider the following SYSEX MIDI message:  F0 7F 7F 04 01 7F 7F F7 This would be stored in a MIDI file as the following series of bytes (minus the delta-timebytes which would precede it):  F0 07 7F 7F 04 01 7F 7F F7 The 07 above is the variable length quantity (which happens to fit in just one byte for thisexample). It indicates that there are seven, following bytes that comprise this SYSEX message. Really oddball midi units send a system exclusive message as a series of small "packets" (witha time delay inbetween transmission of string location]each packet). The first packet begins with an F0, but itdoesn't end with an F7. The subsequent packets don't start with an F0 nor end with F7. The lastpacket doesn't start with an F0, but does end with the F7. So, between the first packet' = s opening F0 andthe last packet's closing F7, there's 1 SYSEX message there. (Note: only extremely poor designs,such as the crap marketed by Casio exhibit such horrid behavior). Of course, since a delay isneeded inbetween each packet, you need to store each packet as a separate event with its owntime in the MTrk. Also, you need some way of knowing which events shouldn'[Start t begin with an F0(ie, all of them except the first packet). So, the MIDI file]redefines a midi status of F7(normally used as an end mark for SYSEX packets) as a way to indicate an event that doesn'tbegin with F0. If such an event follows an F0 event, then it's assumed that the F7 event is thesecond "packet" of a series. In this context, it's referred to as a SYSEX CONTINUATION event.Just like the F0 type of event, it has a variable length followed by data bytes. On the otherhand, the F7 event could be used to store MIDI REALTIME or MIDI COMMON messages. In this case,after the variable length bytes, you should expect to find a MIDI Status byte of F1, F2, F3, F6,F8, FA, FB, FC, or FE. (Note that you wouldn' + t find any such bytes inside of a SYSEX CONTINUATIONevent). When used in this manner, the F7 event is referred to as an ESCAPED event.----<CENTER><FONT COLOR=RED><B>Non-MIDI events</B></FONT></CENTER> A status of FF is reserved to indicate a special non-MIDI event. (Note that FF is used in MIDIto mean "reset", so it wouldn't be all that useful to store in a data file. Therefore, the MIDIfile arbitrarily redefines the use of this status). After the FF status byte is another byte thattells you what <B>Type</B> of non-MIDI event it is. It's sort of like a second status byte. Thenafter this byte is another byte(s -- a variable length quantity again) that tells how many moredata bytes follow in this event (ie, its Length). This Length doesn'[Padding value]t include the FF, Typebyte, nor the Length byte. These special, non-MIDI events are called <B>Meta-Events</B>, andmost are optional unless otherwise noted. The section of this online book entitled "Meta-Events"lists the currently defined Meta-Events. Note that unless otherwise mentioned, more than one ofthese events can be placed in an MTrk (even the same Meta-Event) at any delta-time. (Just likeall midi events, Meta-Events have a delta-time from the previous event regardless of what typeof event that may be. So, you can freely intermix MIDI and Meta events).   ==== Meta-Events in an MTrk ====----===== Sequence Number ===== FF 00 02 <I><FONT COLOR=RED><B>ss ss</B></FONT></I> or...  FF 00 00 This optional event must occur at the beginning of a MTrk (ie, before any non-zerodelta-times and before any midi events). It specifies the sequence number. The two data bytes<I><FONT COLOR=RED><B>ss ss</B></FONT></I>, are that number which corresponds to the <B>MIDICue</B> message. In a format 2 MIDI file, this number identifies each "pattern" (ie, Mtrk) sothat a "song" sequence can use the MIDI Cue message to refer to patterns. If the <I><FONT COLOR=RED><B>ss ss</B></FONT></I> numbers are omitted (ie, the second formshown above), then the MTrk's location in the file is used. (ie, The first MTrk chunk issequence number 0. The second MTrk is sequence number 1. Etc). In format 0 or 1, which contain only one "pattern" (even though format 1 containsseveral MTrks), this event is placed in only the first MTrk. So, a group of format 0 or 1 fileswith different sequence numbers can comprise a "song collection". There can be only one of these events per MTrk chunk in a Format 2. There can be only oneof these events in a Format 0 or 1, and it must be in the first MTrk.----===== Text ===== FF 01 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> Any amount of text (amount of bytes = <I><FONT COLOR=GREEN><B>len</B></FONT></I>) for anypurpose. It's best to put this event at the beginning of an MTrk. Although this text could beused for any purpose, there are other text-based Meta-Events for such things as orchestration,lyrics, track name, etc. This event is primarily used to add "comments" to a MIDI file which aprogram would be expected to ignore when loading that file. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Copyright ===== FF 02 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> A copyright message. It' + s best to put this event at the beginning of an MTrk. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Sequence/Track Name ===== FF 03 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> The name of the sequence or track. It's best to put this event at the beginning of anMTrk. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Instrument ===== FF 04 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> The name of the instrument (ie, MIDI module) being used to play the track. This may bedifferent than the Sequence/Track Name. For example, maybe the name of your sequence (ie, Mtrk)is "Butterfly", but since the track is played upon a Roland S-770, you may also include anInstrument Name of "Roland S-770". It's best to put one (or more) of this event at the beginning of an MTrk to provide the userwith identification of what instrument(s) is playing the track. Usually, the instruments (ie,patches, tones, banks, etc) are setup on the audio devices via <B>MIDI Program Change</B>and <B>MIDI Bank Select Controller</B> events within the MTrk. So, this event exists merely toprovide the user with visual feedback of what instruments are used for a track. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Lyric ===== FF 05 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> A song lyric which occurs on a given beat. A single LyricMetaEvent should contain only one syllable. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Marker =====  FF 06 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> The text for a marker which occurs on a given beat. Marker events might be used to denote a loop start and loop end (ie, where the sequence loops back to a previous event). Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Cue Point===== FF 07 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> The text for a cue point which occurs on a given beat. A Cue Point might be used to denotewhere a WAVE (ie, sampled sound) file starts playing, for example, where the<I><FONT COLOR=RED><B>text</B></FONT></I> would be the WAVE'[String offset s filename. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Program (Patch) Name ===== FF 08 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> The name of the program (ie, patch) used to play the MTrk. This may bedifferent than the Sequence/Track Name. For example, maybe the name of your sequence (ie, Mtrk)is "Butterfly", but since the track is played upon an electric piano patch, you may also include aProgram Name of "ELECTRIC PIANO". Usually, the instruments (ie, patches, tones, banks, etc) are setup on the audio devices via<B>MIDI Program Change</B> and <B>MIDI Bank Select Controller</B> events within the MTrk. So,this event exists merely to provide the user with visual feedback of what particular patch isused for a track. But it can also give a hint to intelligent software if patch remapping needsto be done. For example, if the MIDI file was created on a non-General MIDI instrument, thenthe <B>MIDI Program Change</B> event will likely contain thewrong value when played on a General MIDI instrument. Intelligent software can use theProgram Name event to look up the correct value]'for the <B>MIDI Program Change</B> event. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.----===== Device (Port) Name ===== FF 09 <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>text</B></FONT></I> The name of the MIDI device (port) where the track is routed. This replaces the "MIDI Port"Meta-Event which some sequencers formally used to route MIDI tracks to various MIDI ports (inorder to support more than 16 MIDI channels). For example, assume that you have a MIDI interface that has 4 MIDI output ports. They arelisted as "MIDI Out 1", "MIDI Out 2", "MIDI Out 3", and "MIDI Out 4". If you wished a particularMTrk to use "MIDI Out 1" then you would put a Port Name Meta-event at the beginning of the MTrk,with "MIDI Out 1" as the <I><FONT COLOR=RED><B>text</B></FONT></I>. All MIDI events that occur in the MTrk, after a given Port Name event, will be routed to thatport. In a format 0 MIDI file, it would be permissible to have numerous Port Name events intermixedwith MIDI events, so that the one MTrk could address numerous ports. But that would likely makethe MIDI file much larger than it need be. The Port Name event is useful primarily in format 1MIDI files, where each MTrk gets routed to one particular port. Note that <B>len</B> could be a series of bytes since it is expressed as a variable lengthquantity.----===== End of Track ===== FF 2F 00 This event is <u>not</u> optional. It must be the last event in every MTrk. It's used as a definitive marking of the end of an MTrk. Only 1 per MTrk. ----===== Tempo ===== FF 51 03 <I><FONT COLOR=RED><B>tt tt tt</B></FONT></I> Indicates a tempo change. The 3 data bytes of <B>tt tt tt</B> are the tempo in microseconds per quarter note. In otherwords, the microsecond tempo value tells you how long each one of your sequencer's "quarter notes" should be. For example,if you have the 3 bytes of 07 A1 20, then each quarter note should be 0x07A120 (or 500,000) microseconds long. So, the MIDI file format expresses tempo as "the amount of time (ie, microseconds) per quarter note". <B><FONT COLOR=RED>NOTE:</FONT></B> If there are no tempo events in a MIDI file, then thetempo is assumed to be 120 BPM In a format 0 file, the tempo changes are scattered throughout the oneMTrk. In format 1, the very first MTrk should consist of only the tempo (and time signature) eventsso that it could be read by some device capable of generating a "tempo map". It is best not toplace MIDI events in this MTrk. In format 2, eachMTrk should begin with at least one initial tempo (and time signature) event.----===== SMPTE Offset ===== FF 54 05 <I><FONT COLOR=RED><B>hr mn se fr ff</B></FONT></I> Designates the SMPTE start time (hours, minutes, seconds, frames, subframes) of the MTrk. It shouldbe at the start of the MTrk. The hour should not be encoded with the SMPTE format as it is in<B>MIDI Time Code</B>. In a format 1 file, the SMPTE OFFSET must be stored with the tempomap (ie, the first MTrk), and has no meaning in any other MTrk. The <FONT COLOR=RED><B>ff</B></FONT>field contains fractional frames in 100ths of a frame, even in SMPTE based MTrks which specify a differentframe subdivision for delta-times (ie, different from the subframe setting in the MThd).----===== Time Signature ===== FF 58 04 <I><FONT COLOR=RED><B>nn dd cc bb</B></FONT></I> Time signature is expressed as 4 numbers. <I><FONT COLOR=RED><B>nn</B></FONT></I>and <I><FONT COLOR=RED><B>dd</B></FONT></I> represent the"numerator" and "denominator" of the signature as notated on sheet music. The denominator is anegative power of 2: 2 = quarter note, 3 = eighth, etc. The <I><FONT COLOR=RED><B>cc</B></FONT></I> expresses the number ofMIDI clocks in a metronome click. The <I><FONT COLOR=RED><B>bb</B></FONT></I> parameter expresses the number of notated32nd notes in a MIDI quarter note (24 MIDI clocks). This event allows a program to relate whatMIDI thinks of as a quarter, to something entirely different. For example, 6/8 time with ametronome click every 3 eighth notes and 24 clocks per quarter note would be the followingevent:  FF 58 04 06 03 18 08 <B><FONT COLOR=RED>NOTE:</FONT></B> If there are no time signature events in a MIDI file,then the time signature is assumed to be 4/4. In a format 0 file, the time signatures changes are scattered throughout the oneMTrk. In format 1, the very first MTrk should consist of only the time signature (and tempo) eventsso that it could be read by some device capable of generating a "tempo map". It is best not toplace MIDI events in this MTrk. In format 2, eachMTrk should begin with at least one initial time signature (and tempo) event.----===== Key Signature ===== FF 59 02 <I><FONT COLOR=RED><B>sf mi</B></FONT></I> <I><FONT COLOR=RED><B>sf</B></FONT></I> = -7 for 7 flats, -1 for 1 flat, etc, 0 for key of c, 1 for 1 sharp, etc. <I><FONT COLOR=RED><B>mi</B></FONT></I> = 0 for major, 1 for minor----===== Proprietary Event ===== FF 7F <I><FONT COLOR=GREEN><B>len</B></FONT></I> <I><FONT COLOR=RED><B>data</B></FONT></I> This can be used by a program to store proprietary data. The first byte(s) should be a unique IDof some sort so that a program can identity whether the event belongs to it, or to some otherprogram. A 4 character (ie, ascii) ID is recommended for such. Note that <I><FONT COLOR=GREEN><B>len</B></FONT></I> could be a series of bytes since itis expressed as a variable length quantity.