Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
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.
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.
Ardour - Record, edit, and mix on Linux, Mac OS X, and Windows.
GarageBand - GarageBand is a fully equipped music creation studio for Mac
Bitwig Studio - Bitwig Studio is a multi-platform music-creation system for production, performance and DJing, with a focus on flexible editing tools and a super-fast workflow.