For several chants a midi file is already provided. This is shown through bold print of the reference link in the indexes.
The purpose of these midi files is two-fold. In the first place they can be used to check whether the chant is actually the one you are looking for.
It would have been sufficient (in most cases) to provide for a midi file for each fingerprint.
However, occasionally two different chants may have the same fingerprint, so it helps if each occurence has its own midi file.
Moreover, between chant books there are often subtle differences in ornamentation and harmonisation.
These are the main reasons to provide for a midi file for each reference.
The earliest entries of the index do not yet have midi files (apart from Bennett & Marshall),
since I started off with a different way of entering the fingerprint.
For these the midi files will be added at a later date.
The midi files are created by entering the notes (yes, by hand .... ) into Finale and saving the file as midi.
(The Finale files are also exported as XML from which the fingerprint is obtained by a special program.)
The instrument used for the midi is a recorder (midi program 75).
The recorder ensemble sounds more or less like an organ with only a 4' stop.
This setup makes it easier to distinguish the separate voices, contrary to the midi-provided organ (midi program 20) which synthesizes multiple stops with many overtones.
There are two exceptions to this:
in a few cases, where the chant should be sung unison with a treble descant, the melody is played on a flute (midi program 74), with the descant and the harmony on recorders.
The second case is where the chant must be sung in unison with organ accompaniment (e.g. Daniel Pinkham's chant). There the organ part is played on the midi church organ (program 20), with the melody on a flute.
For questions about the midi files, please contact me at the address below.