From the manual (yes, file names have cryptic meanings):

MGU Files:
A Band-in-a-Box song called “My Song.MGU” will have the associated wave file called “My Song.wav.”

MGX Files:
When a MIDI file is loaded onto the Melody (or Soloist) track, the Track Type for the Melody (or Soloist) gets set to Multi-Track. When the file is saved, the extension will be .MGX

The .SIB file is is a Sibelius music notation file.

The .MXL is a compressed music XML file.


BIAB & RB2024 Win.(Audiophile), Sonar Platinum, Cakewalk by Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Kontakt, Focusrite 18i20, KetronSD2, NS40M Monitors, Pioneer Active Monitors, AKG K271 Studio H'phones