This is wonderful open source DAW for Linux. Very stable especially on Ubuntu and Linux Mint. Best complimented by KXStudio's set of audio apps, including Cadence and Catia.
Good for creating music though a little complicated. I would suggest using LMMS along with it. I'm not really a professional(more a beginner) but starting with this program is a bit hard... But then with time you get used to it.
Ardour is a very powerful free DAW. It's almost the anti-LMMS in that it's great for anything you'd need in terms of recording, mixing, and audio, but is somewhat lacking in MIDI capabilities.