What are MIDI files?

MIDI (which stands for Musical Instrument Digital Interface) is a way of encoding music so that it can be played on a computer. A MIDi file contains a series of instructions which are interpreted by a programme (a MIDI synthesiser programme) which generates musical notes . So a MIDI file might contain instructions equivalent to “Play middle C for 200 milliseconds, then do the same again, then play the G above for 200 milliseconds, then the same again…” which, fed to the synthesiser programme, will produce the first four notes of Ba Ba Black Sheep.

Thus MIDI files are very different in form and function from digital audio files (such as MP3 files), which are digitised recordings of actual performances. They are more like piano rolls, which rely on the machine they are played on (the player piano) to make the actual music.

Compared with digital audio recordings, MIDI files make for a pretty poor listening experience. They convey no nuances of expression, and the tones produced by a MIDI synthesiser programme bear only a vague resemblance to the sounds of real instruments and voices. But for practising, MIDI files have distinct advantages. With the right software you can modify the way the file will sound. You can alter the balance between voices (so that you hear your part more clearly); you can mute any voice or combination of voices (so that you hear only your part); you can even slow the tempo down (or speed it up, if you find that helpful!).


How to play them

Many of the MIDI files available on sites such as CyberBass ( already been modified for choral practice, with a separate file for each part. You can select the alto file, for example, and hear a version of the piece with the alto part amplified and the other parts just loud enough for orientation.

Other sites offer a single file for each piece with the parts evenly balanced. However, with a suitable MIDI synthesiser program you can manipulate these files yourself.

Such a program (for Windows users) is vanBasco’s Karaoke Player, available free from  Mac users may want to try Rondo  - at

To play a MIDI file using vanBasco  you will need to download and save the file on your computer. Then start vanBasco, then drag the midi file onto the “player” window (see below) of vanBasco.

vanBasco consists of several separate modules, of which the really useful ones, for choir practice, are the player, the MIDI output window, and the control. 

The “player” looks like this:

It enables you to play, pause, repeat etc. as you would with a cassette player. It also has a row of buttons at the bottom which make the other modules appear or disappear.

The output module looks like this.

It shows a visual trace for each part as it is being played. Next to each part are two buttons, one red and one grey. The red button mutes the respective part; the grey button boosts it (makes it louder in the mix). In the example, the first voice has been muted and the third boosted. 

First you have to identify which part is yours. This might not be obvious as it probably won’t be labelled “alto” or whatever; it might be labelled “flute1” or “choir oohs” depending on how the file has been set up, but usually it will be in a logical position in the list (for example, second one down of the active voices for the alto part in a SATB arrangement).

The other module that you might find useful is the “control” window, which looks like this:

This enables you to change the tempo, volume, and (should you feel so inclined!) key of the music. Happy practising!


Glyn Jones
January 2014 (A PDF version of this file is available here)

Additions for Mac users courtesy of Katy Payne
January 2014