The Pro Tracks Plus tutorials are MIDI-only and contain no audio. They will need something to produce the MIDI sounds, whether it be a keyboard or rack module hooked up to the MIDI ports of the Omega (recommended), a Soundblaster-compatable internal card with a GM MIDI synth in it (many newer cards do not have this feature), or the virtual DXI built-in to Pro Tracks Plus (you'll have to add this manually and re-route the tutorial tracks through it).