What Is MIDI in Music? A Beginner’s Guide to MIDI Files and Controllers

MIDI stands for Musical Instrument Digital Interface. It is a way for musical devices and software to communicate performance instructions: which notes to play, when to play them and how to respond to controls. A MIDI instrument interprets those instructions and creates sound.

For example, playing a key on a MIDI controller can send a note to a piano instrument in your computer. Change the instrument to a synthesizer and the same performance can play a different sound. The MIDI Association’s overview explains the distinction between the instructions and the audio produced by an instrument.

MIDI vs. audio: what is the difference?

Question	MIDI	Audio
What is stored?	Performance events such as notes and timing in a standard MIDI file.	Recorded or rendered sound as digital samples in a format such as WAV.
How do you hear it?	Send the notes to a software or hardware instrument.	Play the recording through an audio output and speakers or headphones.
What can you edit?	Change individual note pitches, positions and lengths in a compatible editor.	Edit the waveform and apply audio processing; individual notes in a mixed recording are not automatically separate.
Will it sound the same elsewhere?	Not necessarily: instrument sounds and settings can differ.	The recorded sound is contained in the file, though playback equipment and settings still affect what you hear.

MIDI is useful while composing because notes can be rearranged without replaying a part. Audio is useful when you want to preserve the sound of a particular instrument, voice, effect or mix. Many projects use both. Learn how they fit into a timeline in our DAW guide.

How MIDI notes work

A note message identifies a pitch and when a note begins; another message ends it. A performance can also include velocity, which a receiving instrument may use to change loudness or tone. Sustain-pedal, pitch-bend and other controller messages add expression. The exact response depends on the instrument and its settings; see the MIDI Association’s message guide.

Imagine drawing a C4 note on a piano roll and extending it for one beat. Moving the rectangle changes when it plays; raising it changes its pitch; extending it changes its length. Adjusting its velocity may make a piano patch sound softer or harder. This does not edit a recorded piano waveform: it changes the instructions sent to the instrument.

What is a MIDI file?

A Standard MIDI File, commonly ending in .mid or .midi, stores a sequence of MIDI events that compatible software can read. It can be useful for sharing an arrangement or moving notes between applications. It does not contain a recording of the original singer, piano or synthesizer.

A MIDI file may include instrument-selection information, but another device may interpret that information with different available sounds. General MIDI defines a common set of instrument assignments for compatible equipment; do not assume every synthesizer or plugin follows those assignments. If the exact sound matters, share an audio render as well as the MIDI and check the recipient’s software.

Make your first MIDI part

1. Open a MIDI-capable DAW. Create a project and choose a working audio output for headphones or speakers. MIDI features differ between applications and editions.
2. Add an instrument track. Load a software piano or synthesizer on the track. A controller by itself may not have speakers or make sound.
3. Enter a few notes. Open the piano roll and draw a short melody, or connect a MIDI keyboard and record a performance. For a keyboard, select it as the track’s MIDI input and enable monitoring or recording as your DAW requires.
4. Play and edit. Move one note, change its length and adjust its velocity. Switch the instrument preset to hear how the same notes can produce a different sound.
5. Save and export. Save the editable project. Export MIDI if you want to move the notes to compatible software; render audio if you need a playable recording of the chosen sound. Listen to the exported file.

Why can’t I hear my MIDI?

• No instrument: Place a software instrument on the MIDI track or route the track to a compatible external sound source.
• Wrong input or monitoring: Confirm the controller appears in the DAW’s MIDI settings, select it for the track and enable the appropriate monitoring or record setting.
• Wrong output or channel: Check the instrument’s MIDI channel when using hardware, and verify the DAW’s audio output, instrument level and speaker or headphone connection.
• Delayed response: Audio buffering and processing can add latency. Review the audio device and buffer settings; lower buffers can reduce delay but may cause glitches if the computer cannot keep up. Ableton explains latency and its tradeoffs.

Can you convert a recording to MIDI?

Some software estimates notes from an audio recording, but it cannot recover the original MIDI perfectly. A clear single melody is often a more practical starting point than a full mix. Compare the detected notes, timing and lengths with the original and correct mistakes by ear. See how to convert audio to MIDI for software options and an editing workflow.

To test a small section, use the audio trimmer to save a supported short MP3 or WAV excerpt, then import that excerpt into separate transcription software. The trimmer does not convert audio into MIDI.

Common questions

Do I need a MIDI keyboard?

No. Many DAWs let you draw notes in a piano roll, and some can use a computer keyboard. A MIDI controller is useful for playing parts by hand, but it is optional.

Is MIDI a type of audio file?

A Standard MIDI File stores musical events, not an audio recording. To make a WAV or MP3, play the MIDI through an instrument and render or record its audio output.

Does MIDI record my voice?

A microphone records audio. MIDI can represent notes estimated from a voice recording by separate transcription software, but those notes do not contain the voice’s original sound.