I take it that youre talking about a type 1 midi file, i.e. a file with multiple tracks (as in a separate track for each instrument).

There are a number of different 'sequencer' software packages, that will have an option that displays all the tracks on one screen. Maybe the 'Piano Roll' display will be the best one. These may well have an option to select part of the file, i.e. all tracks but only a range of measures. Then you could save the selected part as a new file, or delete the rest (having saved the complete file as a backup) and the save the remaining part. This will get more complicated though if you want to do the same thing for - say - the second block as there may be important MIDI instructions at the start without which the later parts may no longer work correctly.

Which software do you use now? Does this have such an option?

Geoff

Cakewalk has an option to split files at the current cursor location. You could split, then delete what you don't need.

It also has an option that lets you select by measure, then you can copy the selected measures in to a new file.

Jason might have said this, but CakeWalk is available for free download, so you can get the software and check it out and see if it does what you want. Sounds like to could do so. Like anything else, you may have to experiment to find the most convenient way of doing things.

Lots of help for CW available via the web.

You seemed to be asking about running one 'job' to split the file into multiple sections? This may not be practical, for the reason that I suggested. MIDI data is handled strictly in the order that it occurs, and various settings (instruments, tempo, volume to name but a few) then affect all the data that follows. If you chop the file up, then various settings will become detached from some (or even ALL) of the notes that they should apply to. Your music will no longer play correctly?

Ask further if you hit any snags.

Geoff