Rosegarden is a free and open source digital audio workstation software for linux. It is a great free music composition and editing software. You can also use as a audio and midi sequencer and musical notation software. It uses the JACK audio sever, ALSA sound drivers and DSSI synth plugins. It comes with unlimited tracks and built-in database of real-world instruments. It supports more than 100 midi playback devices. You can record and mix the audio using samples and effects in this tool. It uses LADSPA plugin API.