Cubase - Cubase is one of the world’s most powerful music creation software packages. From first idea to finished recording, Cubase helps you to make outstanding music.
Clyp - Clyp is the easiest way to record, upload and share audio. No account required.
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Audio Hijack - Record any audio, with Audio Hijack!
FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!