Midi is a format that was defined in 1982 to provide a standard way for primarily electronic keyboards to comunicate with and cause synthesisers to play music. Basically midi files are a sequence of messages such as "start playing a particular note at a particular volume on a particular channel", followed an appropriate time later with, "stop playing the note". Each musical part will have a channel and there can normally be up to 16 channels. Each channel is usually associated with a particular synthesised voice, piano, violin, choir, etc.

Midi became popular with computers once they acquired sound facilities. Midi files are quite small so are easily transferred between machines. Midi can be recorded on computer by capturing the midi signals from a keyboard when someone plays the music. Software exists which allows someone to play each part of a multi-part piece separately and they can then be combined and given their appropriate voice and so create quite complicated "recordings" of pieces of music. A great deal of the midi music available on the internet has been produced this way.

An alternative way of creating midi files is to use music notation software. These are rather like "word processors" for music. Converting music in conventional notation but in computerised form to midi is relatively straight forward but, since midi may not know anything about key signatures, time signatures, bar lines, accents or phrasing marks, etc. the reverse process of turning a stream of note-on and note-off commands into accurate sheet music is not totally possible. Nevertheless, many midiplayer programs, by making a number of assumptions make a pretty good stab at it.

One of the things midi-music conversions very rarely even attempt, since there is no standard way of expressing it in the midi protocol, are conventional transpositions. For example, the music for tenors is usually written on the treble clef but the notes are sung an octave lower than written. Programs that convert midi to notation will often render the tenor line in concert pitch on a grand staff, with both treble and bass clef. Others will choose which ever clef seems most appropriate. Also because of the limitations to midi it is often almost impossible to tell the difference between, say, a quaver followed by a quaver rest and a crochet played staccato. The music notation scores produced by converting midi are therefore slightly unreliable even if the music sounds reasonably accurate.

The midi files made available here have been produced by using a musical notation program called MOZART. This allows the score to be reproduced on the computer display more or less exactly as it would be in the printed score, complete with dynamics, phrase marks, accents and lyrics. The appropriate general midi instruments can be attached to each strand of the music and this can be played back with a karaoke type line indicating the position in the music. This can be done either via the full Mozart program, which is not free, or via a free viewer program that can be down loaded from the MOZART website. The playback and display produced this way can be highly accurate and precise.  Alternatively these MOZART (.mz) files can be exported to midi (.mid) format and played via software like midiplay. Since MOZART produces printable scores that are a good representation of the original music, music that is still in copyright cannot be placed directly on this website in .mz form.