Seq24

Seq24 is a software MIDI music sequencer that runs under Linux and Microsoft Windows. Written in C++, it is designed to be simple to use and appropriate for live performance.
Distributed under the terms of the GNU General Public License v2, Seq24 is free software.
Seq24 is intended to be similar to hardware sequencers/samplers such as Akai's MPC line of instruments. It works by sequencing smaller sequences or loops of MIDI notes and performance information into larger music sequences in a manner similar to the way in which Sony's Acid software is used to sequence audio clips. In order to do this, it has a patterns panel, a pattern editor and a song editor. Sequences are saved as Standard MIDI file format, type 1.
While developed from 2002-2006 by Rob Buse, a team (calling themselves simply 'Seq24team') picked up the project in 2008 with Rob's blessing, and resumed work with release 0.8.8.