A couple of random possibilities...

Are you trying to export a song made with Real Tracks or a MIDI style?

MIDI files are amazingly small, most songs I do are well under 1 Meg often under 100 K in size.

Have you tried importing it into another DAW?

If you don't have another DAW can you play it in Microsoft's Media Player? If it is a MIDI file, it should play in Media player using the lame but usable sounds in Microsoft's software synth.

If you can or cannot import it into another DAW or play it in Media Player it will let you know if the problem is associated with BiaB or your DAW.

Type 1 MIDI is the preferred way to save it if you are going to import into a DAW. I've done thousands this way with no problem. They have all been MIDI styles though. I've never tried to export a Real Track as MIDI because I don't think it would transfer properly. (Please correct me if that's wrong.)

Insights and incites by Notes

Bob "Notes" Norton smile Norton Music
https://www.nortonmusic.com

100% MIDI Super-Styles recorded by live, pro, studio musicians for a live groove
& Fake Disks for MIDI and/or RealTracks