I get this error when trying to import song parts in MIDI files made in PreSonus Studio One.The same MIDI imports fine to GarageBand, only with the piano sound, but the notes are there. Any Ideas?
Most likely MIDI files you are trying to import do not contain a drum track.
BeatBuddy currently is designed to play a drum track (MIDI channel 10) exclusively.
Also keep in mind, that only a subset of drum MIDI notes are supported!
You can also upload a sample MIDI file here for me to check.
Those ARE drum tracks prepared in PreSonus StudioOne, where they play just fine, but I also thought there may be some channel/instrument assignment disconnect; the same files play in GarageBand but as piano, and when I change the sound to a drum kit, some instruments change. Here are two test fills I wanted to import - and I deeply appreciate your assistance with this.
N.B.: PreSonus offers no options for exporting such .mid files, so if you have any ideas about how to convert/adapt them, that would be a life-saver.
Your MIDI files are not standard. Most likely (as you say it yourself), the MIDI files are missing headers with information about track channel. I suspect they also have some data specific to your PreSonus StudioOne, so no other program will ever be able to play them.
I have no idea of PreSonus StudioOne, I use Guitar Pro 5.2 instead. If you wish to continue using your program, I’d recommend seeking help from its developers, sorry 
That’s a great start, thanks for your help. Merry Christmas (or anything you celebrate these days) & happy 2015!