Virtual Audio Cable - Ever wanted to record your speaker output? (loopback) This is for you.
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!
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.
JACK Audio Connection Kit - JACK Audio Connection Kit|Home
Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.