Jim, I use Audacity: http://audacity.sourceforge.net/

I work with mostly MIDI in BiaB, transfer those MIDI tracks to Sonar, save the finished Sonar file as a wav then use Audacity to convert it to an MP3. Audacity has many MP3 compression options and effects. Although I use a PC I see that Audacity is available for a Mac and probably offers the same options there. Also Audacity is free so it costs nothing to try it.

I hope this helps.

Whenever I get something stuck in the back of my throat, I dislodge it by drinking a beer.
It's called the Heineken Maneuver.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware