From Paul Giblock:
LMMS is a free cross-platform alternative to commercial program like FL Studio, which allow you to produce music with your computer. This includes the creation of melodies and beats, the synthesis and mixing of sounds, and arranging of samples. LMMS can also connect to any of your MIDI devices and allow you to perform live, all in a user-friendly and modern interface.
What's new in this version:
Version 0.4.15 has fixed freeze when forwarding MIDI events to instrument.