Melys is a MIDI sequencer application for ALSA. It records, plays back, and saves to a MIDI file or to an XML-based format. There is a track view where you can arrange parts using drag-and-drop and a piano-roll view where the same can be done with notes. There is also a graphical tempo view where the tempo of the song can be changed. Multiple files can be open at once, and notes can be dragged between them. It is written in C and uses the GNOME/Gtk+ widget sets.
