Linux MultiMedia Studio, now known as LMMS, is a free audio editor software, which can be a superb-enough alternative for FL Studio, but completely free to use! LMMS offers a huge number of impressive features as a whole, including the FX Mixer, Automation Editor, support for MIDI Keyboard, some in-built audio effects and instruments and compatibility with some popular standards in Digital Music Production and editing. The UI of LMMS is truly professional one and the availability of plug-ins can take the productivity to a new extent too. so, when you are not ready to pay, LMMS is a solution you can depend upon for easier editing and mixing of music. Of course, there are a few perks of being an Open Source project, such as wide range of support. Also, to be noted, LMMS is made by a set of musicians!
Price: Free Availability: Microsoft Windows, Mac OS X and Linux.