Sound effects, music samples and MIDI files

Digital audio used in web pages, presentations and multimedia projects generally falls into a few broad categories: recorded sound effects, short musical samples, and sequenced music stored as MIDI. Sound effects are brief recordings of real or synthesised events — footsteps, animal calls, machinery, weather, or human voices — that designers add to reinforce on-screen action. Music samples are short excerpts of melody, rhythm or instrument tones that can be looped or layered to build a soundtrack.

Recorded audio is most often distributed as WAV or MP3 files. A WAV file typically stores uncompressed pulse-code-modulated samples, preserving full quality at the cost of large file sizes. MP3 uses lossy compression that discards information the ear is less likely to notice, producing much smaller files suitable for downloading and streaming. The trade-off between fidelity and size is the main reason a project might choose one format over the other.

MIDI (Musical Instrument Digital Interface) works differently. Rather than storing recorded sound, a MIDI file records performance instructions — which note is played, when, how loudly, and on which instrument — that a synthesiser or sound card renders into audio. Because it stores instructions instead of waveforms, a MIDI file is very compact, but the way it sounds depends on the playback device. MIDI is widely used for background music, electronic instruments and computer music composition, while sampled instrument tones let composers reproduce real instruments within software.

Frequently asked questions

What is the difference between a WAV and an MP3 file?

WAV usually stores uncompressed audio at full quality and large size, while MP3 uses lossy compression to make much smaller files by discarding less audible detail.

How is a MIDI file different from a recorded sound file?

A MIDI file contains performance instructions such as notes and timing rather than recorded sound, so a synthesiser must generate the audio when it is played.

Why are MIDI files so small?

They store only instructions for instruments rather than the audio waveform itself, so a few kilobytes can describe a whole piece of music.