Hexadecimal Representation of MIDI Note On Messages

This article provides an overview of the hexadecimal structure used in a standard Musical Instrument Digital Interface (MIDI) Note On message. It breaks down the standard three-byte sequence—the status byte, the note number, and the velocity value—explaining the specific role and hexadecimal range of each byte along with practical examples for implementation.

A standard MIDI Note On event is a channel voice message made up of three successive bytes, formatted as:

9n kk vv

Byte 1: The Status Byte (9n)

The status byte indicates the action to be performed and the MIDI channel it applies to.

• Command Nibble (9): The first nibble (the most significant 4 bits) is always 9, which defines the message as "Note On."
• Channel Nibble (n): The second nibble specifies the MIDI channel from 0 to 15 (representing Channels 1 to 16 in hexadecimal).
• Hex Range: 0x90 to 0x9F (where 0x90 corresponds to Channel 1 and 0x9F corresponds to Channel 16).

Byte 2: The Note Number (kk)

The second byte identifies the pitch of the note being played.

• Range: MIDI notes range from 0 to 127 in decimal.
• Hex Range: 0x00 to 0x7F.
• Example: Middle C (MIDI note 60) is represented as 0x3C.

Byte 3: Velocity (vv)

The third byte indicates how hard the key was struck, which usually controls volume or timbre.

• Range: Velocity values range from 0 to 127 in decimal.
• Hex Range: 0x00 to 0x7F.
• Special Case: A velocity of 0x00 is defined by the MIDI specification as a "Note Off" command for that specific pitch, allowing instruments to release the note without sending a separate Note Off status byte (0x8n).

Practical Example

To trigger Middle C (note 60) on MIDI Channel 1 at maximum velocity (127):

• Status Byte: 0x90 (Note On, Channel 1)
• Note Byte: 0x3C (Note 60 / Middle C)
• Velocity Byte: 0x7F (Velocity 127)

The complete hexadecimal message transmitted across the MIDI line is: 90 3C 7F.