MIDI and MP3: What's the Difference?

The hottest word in popular culture is now MP3. Music company executives fear it, students love it, and journalists can't say enough about it, even if they don't understand it. So, what is it exactly, and why is it so much bigger than MIDI?

In a nutshell

An MP3 file is just an audio file that has been compressed (made smaller) so that it can be sent easily over the Net. An uncompressed music file, like that found on a CD, can be 30 or 40 megabytes or much larger. MP3's are typically one-tenth this size, with only a slight loss in quality.

MIDI files, on the other hand, do not contain actual audio. Instead, the music sequence is recorded as a series of numbers which explain how the music is to be played back. The advantage is that MIDI files are very small, but the sound is totally dependent on the output device (usually the sound card in the computer).

The boring, technical definitions

MP3 is short for MPEG1 Layer 3. MPEG stands for Moving Pictures Experts Group, an organization working under the joint direction of the International Standards Organization (ISO) and the International Electro-Technical Commission (IEC). This group devises standards for the coding of moving pictures and audio. MPEG audio files are compressed, and are typically one-tenth the size of uncompressed files (a CD track, or WAV or AIF file is uncompressed audio).

MIDI stands for Musical Instrument Digital Interface, and was first introduced in 1983. This is not actually an audio format, but rather a protocol  by which various electronic musical instruments, including sound cards in computers, connect to and interact with each other. However, many people use the term "MIDI" to refer to files (sequences) produced by MIDI devices. (To learn more, see my previous column entitled Increase Your MIDI IQ). Unlike the following audio formats, MIDI files do not actually contain music recordings, but rather a set of instructions on how to play a tune. Think of a piano roll, which contains the information on how to play a piece, but can't produce music without a player piano.

What this means to you

MIDI files are very small, and therefore excellent for use in Web pages and other applications. Just a few seconds of download time, even on a slow connection, can yield several minutes of listening pleasure. MIDI files will play on most browsers without having to install a third-party plug-in. These files are also much easier to edit than other types.

As mentioned before, the main disadvantage of MIDI is that the quality of playback is  dependent on the playback device (sound card or synthesizer). A MIDI sequence that sounds great on a high-end card may sound terrible on a cheap one. Also, MIDI is for instrumentals only, not vocals. Most MIDI sequencing programs such as Cakewalk and Cubase can combine MIDI with digital audio so that vocals or non-MIDI instruments can be incorporated. However, these are all proprietary formats, so if you record such a file with Cakewalk the tune can be played back only with Cakewalk.