MIDI stands for Musical Instrument Digital Interface, and it is a standard way for computers, keyboards, drum pads, and synthesizers to communicate. It matters because it lets one device control another without sending actual recorded sound. A laptop can tell a keyboard which note to play, how hard it was pressed, and when to stop.
This makes MIDI a powerful tool for composing, performing, and controlling music technology.
Key Facts
- MIDI sends performance instructions, not audio waveforms.
- A Note On message tells an instrument to start a note, and a Note Off message tells it to stop.
- Middle C is usually MIDI note number 60.
- Velocity usually ranges from 0 to 127 and often controls loudness or intensity.
- One MIDI channel can carry messages for one instrument part, and standard MIDI has 16 channels.
- Frequency for equal-tempered notes can be calculated with f = 440 × 2^((n - 69)/12), where n is the MIDI note number.
Vocabulary
- MIDI
- MIDI is a digital communication standard that sends musical instructions between electronic instruments, computers, and controllers.
- Note On
- A Note On message tells a MIDI device to begin playing a specific note with a specific velocity.
- Velocity
- Velocity is a MIDI value, usually from 0 to 127, that represents how strongly a note was played.
- Synthesizer
- A synthesizer is an electronic instrument that creates sound, often in response to MIDI messages.
- MIDI Channel
- A MIDI channel is a numbered pathway that helps separate messages for different instruments or parts.
Common Mistakes to Avoid
- Thinking MIDI is sound, but MIDI contains instructions such as note number, timing, and velocity rather than an audio waveform.
- Confusing velocity with speed, but MIDI velocity usually describes how hard a key was struck, not how fast the note travels.
- Forgetting Note Off messages, which is wrong because a synthesizer may keep sounding a note until it receives an instruction to stop.
- Assuming every MIDI device sounds the same, but the final sound depends on the instrument, synthesizer patch, or software receiving the MIDI data.
Practice Questions
- 1 A MIDI melody uses notes 60, 62, 64, 65, and 67. If note 60 is middle C, identify the solfege or scale-degree pattern in a C major scale.
- 2 A keyboard sends a Note On message for note 69 with velocity 100. Using f = 440 × 2^((n - 69)/12), what frequency should a synthesizer play for note 69?
- 3 A laptop plays a MIDI file through two different synthesizer sounds, one piano and one trumpet. Explain why the notes and rhythm can stay the same while the sound quality changes.