LMMS is a free open source program which gives you a fully featured music recording studio in a box. It runs on both Windows and Linux and features a song editor, bass-line editor, piano roll sequencer and compatibility with a shed load of effects like VST, SoundFont et al. It’s fast, 64 track and nice people, nice. Why spend tons of money, when this kind of stuff is around?
LMMS is a free cross-platform alternative to commercial programs 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. You can have fun with your MIDI-keyboard and much more; all in a user-friendly and modern interface.