Audacity tutorial: Converting to mp3 or AAC and other formats, example: Matthew Smith - epic orchestral synth music for film and game effects; Buanzo's LAME mp3 library
Howto: Capture/Record live streaming audio on Mac OS X (Leopard, Snow Leopard, Lion, Mountain Lion, Mavericks, Yosemite, El Capitan) | Manoranjan's Tech blog