controlchanging

Control changing, in the context of music technology, refers to the use of MIDI Control Change messages to alter parameters in real time. It is the primary mechanism by which a performer or a sequencer can modulate sounds, effects, or mixing parameters without directly triggering notes.

A Control Change message is part of MIDI channel voice data. It operates on a specific MIDI channel (1 through 16) and consists of a status byte indicating the channel, followed by two data bytes: the controller number (0–127) and the value (0–127). There are 128 standard controllers, and many devices assign familiar purposes to common numbers, such as 7 for volume, 10 for pan, 11 for expression, and 64 for sustain. The same controller number can be mapped to different parameters by different devices or software.

Resolution and extensions: most controllers transmit 7-bit values, but higher resolution can be achieved by pairing two Control Change messages that carry the same controller number with separate data bytes (often referred to as MSB/LSB pairs) to produce a 14-bit value. This is commonly used for precise parameter control in professional setups.

Applications: Control Change messages are widely used with hardware controllers—knobs, faders, pedals—and with software in digital audio workstations to automate or perform live parameter changes. They enable expressive dynamics, filter sweeps, volume automation, panning, and many other real-time effects, often in combination with other MIDI messages such as Note On/Off, Program Change, or NRPN/RPN sequences.

History and standards: Control Change messages are part of the MIDI 1.0 specification, established in the early development of the MIDI standard. They remain a fundamental element of MIDI sequencing and performance workflows.