Note Off Event
The Note Off Event is used to signal when a MIDI key is released. These events have two parameters identical to a Note On event. The note number specifies which of the 128 MIDI keys is being played and the velocity determines how fast/hard the key was released. The note number is normally used to specify which previously pressed key is being released and the velocity is usually ignored, but is sometimes used to adjust the slope of an instrument's release phase.

Note On Event
The Note On Event is used to signal when a MIDI key is pressed. This type of event has two parameters. The note number that specifies which of the 128 MIDI keys is being played and the velocity determines how fast/hard the key is pressed. The note number is normally used to specify the instruments musical pitch and the velocity is usually used to specify the instruments playback volume and intensity.

Note Aftertouch Event
The Note Aftertouch Event is used to indicate a pressure change on one of the currently pressed MIDI keys. It has two parameters. The note number of which key's pressure is changing and the aftertouch value which specifies amount of pressure being applied (0 = no pressure, 127 = full pressure). Note Aftertouch is used for extra expression of particular notes, often introducing or increasing some type of modulation during the instrument's sustain phase.

Controller Event
The Controller Event signals the change in a MIDI channels state. There are 128 controllers which define different attributes of the channel including volume, pan, modulation, effects, and more. This event type has two parameters. The controller number specifies which control is changing and the controller value defines it's new setting.

Below is a list of the defined MIDI controller types.

Program Change Event
The Program Change Event is used to change which program (instrument/patch) should be played on the MIDI channel. This type of event takes only one parameter, the program number of the new instrument/patch.

Channel Aftertouch Event
The Channel Aftertouch Event is similar to the Note Aftertouch message, except it effects all keys currently pressed on the specific MIDI channel. This type of event takes only one parameter, the aftertouch amount (0 = no pressure, 127 = full pressure).

Pitch Bend Event
The Pitch Bend Event is similar to a controller event, except that it is a unique MIDI Channel Event that has two bytes to describe it's value. The pitch value is defined by both parameters of the MIDI Channel Event by joining them in the format of yyyyyyyxxxxxxx where the y characters represent the last 7 bits of the second parameter and the x characters represent the last 7 bits of the first parameter. The combining of both parameters enables high accuracy values (0 - 16383). The pitch value affects all playing notes on the current channel. Values below 8192 decrease the pitch, while values above 8192 increase the pitch. The pitch range may vary from instrument to instrument, but is usually +/-2 semi-tones.

Sequence Number
This meta event defines the pattern number of a Type 2 MIDI file or the number of a sequence in a Type 0 or Type 1 MIDI file. This meta event should always have a delta time of 0 and come before all MIDI Channel Events and non-zero delta time events.

Text Event
This meta event defines some text which can be used for any reason including track notes, comments, etc. The text string is usually ASCII text, but may be any character (0x00-0xFF).

Copyright Notice
This meta event defines copyright information including the copyright symbol © (0xA9), the year and the author. This meta event should always be in the first track chunk, have a delta time of 0 and come before all MIDI Channel Events and non-zero delta time events.

Sequence/Track Name
This meta event defines the name of a sequence when in a Type 0 or Type 2 MIDI file or in the first track of a Type 1 MIDI file. It defines a track name when it appears in any track after the first in a Type 1 MIDI file. This meta event should always have a delta time of 0 and come before all MIDI Channel Events and non-zero delta time events.

Instrument Name
This meta event defines the name of an instrument being used in the current track chunk. This event can be used with the MIDI Channel Prefix meta event to define which instrument is being used on a specific channel.

Lyrics
This meta event defines the lyrics in a song and are usually used to define a syllable or group of works per quarter note. This event can be used as an equivalent of sheet music lyrics or for implementing a karaoke-style system.

Marker
This meta event marks a significant point in time for the sequence. It is usually found in the first track chunk, but may appear in any one. This event can be useful for marking the beginning/end of a new verse or chorus.

Cue Point
This meta event marks the start of some type of new sound or action. It is usually found in the first track chunk, but may appear in any one. This event is sometimes used by sequencers to mark when playback of a sample or video should begin.

MIDI Channel Prefix
This meta event associates a MIDI channel with following meta events. It's effect is terminated by another MIDI Channel Prefix event or any non- Meta event. It is often used before an Instrument Name Event to specify which channel an instrument name represents.

End Of Track
This meta event is used to signal the end of a track chunk and must always appear as the last event in every track chunk.

Set Tempo
This meta event sets the sequence tempo in terms of microseconds per quarter-note which is encoded in three bytes. It usually is found in the first track chunk, time-aligned to occur at the same time as a MIDI clock message to promote more accurate synchronization. If no set tempo event is present, 120 beats per minute is assumed. The following formula's can be used to translate the tempo from microseconds per quarter-note to beats per minute and back.

MICROSECONDS_PER_MINUTE = 60000000

BPM = MICROSECONDS_PER_MINUTE / MPQN
MPQN = MICROSECONDS_PER_MINUTE / BPM


SMPTE Offset
This meta event is used to specify the SMPTE starting point offset from the beginning of the track. It is defined in terms of hours, minutes, seconds, frames and sub-frames (always 100 sub-frames per frame, no matter what sub-division is specified in the MIDI header chunk). The byte used to specify the hour offset also specifies the frame rate in the following format: 0rrhhhhhh where rr is two bits for the frame rate where 00=24 fps, 01=25 fps, 10=30 fps (drop frame), 11=30 fps and hhhhhh is six bits for the hour (0-23). The hour byte's top bit is always 0. The frame byte's possible range depends on the encoded frame rate in the hour byte. A 25 fps frame rate means that a maximum value of 24 may be set for the frame byte.

Time Signature
This meta event is used to set a sequences time signature. The time signature defined with 4 bytes, a numerator, a denominator, a metronome pulse and number of 32nd notes per MIDI quarter-note. The numerator is specified as a literal value, but the denominator is specified as (get ready) the value to which the power of 2 must be raised to equal the number of subdivisions per whole note. For example, a value of 0 means a whole note because 2 to the power of 0 is 1 (whole note), a value of 1 means a half-note because 2 to the power of 1 is 2 (half-note), and so on. The metronome pulse specifies how often the metronome should click in terms of the number of clock signals per click, which come at a rate of 24 per quarter-note. For example, a value of 24 would mean to click once every quarter-note (beat) and a value of 48 would mean to click once every half-note (2 beats). And finally, the fourth byte specifies the number of 32nd notes per 24 MIDI clock signals. This value is usually 8 because there are usually 8 32nd notes in a quarter-note. At least one Time Signature Event should appear in the first track chunk (or all track chunks in a Type 2 file) before any non-zero delta time events. If one is not specified 4/4, 24, 8 should be assumed.

Key Signature
This meta event is used to specify the key (number of sharps or flats) and scale (major or minor) of a sequence. A positive value for the key specifies the number of sharps and a negative value specifies the number of flats. A value of 0 for the scale specifies a major key and a value of 1 specifies a minor key.

Sequencer Specific
This meta event is used to specify information specific to a hardware or software sequencer. The first Data byte (or three bytes if the first byte is 0) specifies the manufacturer's ID and the following bytes contain information specified by the manufacturer. The individual manufacturers may document this information in their respective manuals.

Normal SysEx Events
These are the most common type of SysEx event and are used to hold a single block of manufacturer specific data. The first byte is always 0xF0 and the second is a variable-length value that specifies the length of the following SysEx data in bytes. The SysEx data bytes must always end with a 0xF7 byte to signal the end of the message.

Divided SysEx Events
A large amount of SysEx data in a Normal SysEx Event could cause following MIDI Channel Events to be transmitted after the time they should be played. This will cause an unwanted delay in play back of the following events. The second type of SysEx Events solve this problem by allowing a large amount of SysEx data to be divided into smaller blocks, transmitted with a delay between each division to allow the transmission of other MIDI events in order to prevent congesting of the limited MIDI bandwidth. The initial Divided SysEx Event follows the same format as a Normal SysEx Event with the exception that the last data byte is not 0xF7. This indicates the the SysEx data is not finished and will be continued in an upcoming Divided SysEx Event. Any following Divided SysEx Events before the final one use the a similar format as the first, only the start byte is 0xF0 instead of 0xF7 to signal continuation of SysEx data. The final block follows the same format as the continuation blocks, except the last data byte is 0xF7 to signal the completion of the divided SysEx data.

Authorization SysEx Events
The last type of SysEx Event authorizes and enables the transmission of special messages such as Song Position Pointer, MIDI Time Code and Song Select messages. These SysEx Events use the event type value 0xF7.