Problems with the design of a MIDI editor

Anacrusis and count-in beats

Producing count-in beats seems to be a rather simple problem: put the MIDI events (normally event_on event_off events on channel 10) in front of the MIDI file and play that file. This was my first naive approach. You will find that this is not a satisfying approach with many MIDI files.

For scores starting with an anacrusis some usual MIDI converters (I use the MIDI converter in Capella V4.0) generate rests in front of a MIDI score - even if you don't enter rests in the score:

This is normally not a problem - both notations and MIDI renditions are valid. It may however be a problem if you add count-in beats in front of the MIDI tune: should the count-in beats replace the rests or leave the rests intact? I guess that every normal musician agrees that the count-in beats replace (overwrite) the rests. Things may even be more complex: the sum of rests may be so small that a single count-in beat cannot fill this measure!.

When adding count-in beats a designer for a MIDI editor must proceed as follows:

• Find the first real note event (skip rests athe start of a tune)
• Get the last measure events (saying 3/4, 4/4, 6/8 etc.) before the first note event - the duration of the count-in beats depends on this mesaure event
• Insert the count-in beats before this first note event starting with timestamp 0
• Correct the timestamps for the first note event and all other events

The bitter consequence is thus: it is not possible to design an algorithm that produces correct count-in events for all MIDI files.

Even if you succeed to place the count-in beats correctly in the MIDI file some problems may still remain. The musician cannot be forced to specify the "usual" number of count-in beats. In our notation sample above this would be 3 or 7 count-in beats - he can also specify 5 or 6 or.... if he likes this. You (being the designer of the MIDI editor) will now have the problem that the bar/beat count may be incorrect - which may lead to an even more complex algorithm just to produce count-in beats.

Let me remember that - even if you have solved all these problems - some questions remain open:

• Should the count-in beats remain in the MIDI file when it is saved?
• What do do with some special count-in schemas? Jazz musicians count in following the schema "1 2|1 2 3 4|" (the first bar has half notes) whereas classical musicians just count "1 2 3 4 | 1 2 3 4"