MID to MP3

In the vast array of audio formats, MIDI is something special: while MP3, WAV, FLAC and all the others store finished audio recordings, a MIDI file only contains instructions: which note is played when, for how long, how loud and with which instrument. You could also say that MIDI is the score and MP3 is the recording of the orchestra.

A brief overview of the history of MIDI

The MIDI standard was created in 1983 as the result of an extraordinary collaboration. Synthesiser manufacturers such as Roland, Yamaha and Korg, who were actually competitors, agreed on a common protocol. The goal was to enable keyboards from different manufacturers to communicate with each other. A Roland synth should be able to control a Yamaha expander without the musician having to translate between them.

MIDI was therefore originally a hardware protocol and not a file format. It was only later that the idea arose to record these control commands and store them in files. The result was relatively small files: a complete symphony in just a few kilobytes (of course, you have to be able to get it on paper). In the days of 56k (or even slower) modems, that was worth its weight in gold.

… that's why MIDI sounds different everywhere

Because MIDI is not a finished recording but only a list of instructions, MIDI is "played" or interpreted differently on every device and by every piece of software. A MIDI file only says: "Now play a piano, note C4, medium volume." How this piano sounds is determined by the synthesiser or software that plays the MIDI. To prevent every manufacturer from assigning their own instrument numbers, the General MIDI (GM) standard was introduced in 1991. It specifies that instrument 1 is always an acoustic piano, instrument 25 is always a nylon-string guitar, and instrument 41 is always a violin. This is how a MIDI file sounds, at least with the right instruments – even if not identically.

Today, the actual sound of a MIDI file usually comes from so-called sound fonts. These are collections of audio samples, real recordings of instruments. The larger and higher quality the sound font, the better the result.

Conversion from MID to MP3

When converting to MP3, the MIDI file is essentially "played in". A software synthesiser reads the instructions and uses them to generate a real sound output, which is then saved as an MP3 file. We use TiMidity together with the Fluid R3 soundfont for the conversion, among other things. This delivers solid results with a pleasant sound.