seq24 is a MIDI sequencer. It has a simple user interface. MIDI ".mid" files are the native file format for seq24.
How to setup seq24
seq24 is a sequencer only. To be able to listen to your music as you create it, you will need a MIDI device installed on your computer. Follow the instructions on the timidity wiki page to easily setup a software MIDI device. Then, when using seq24, (you will learn more about this in external documentation) select one of the "TiMidity ports" in the track editor to connect to a MIDI device. For example, on my computer, one of the devices is " 128:0 (TiMidity port 0)".
How to use seq24
The documentation for seq24 can be found in the seq24 manual. Please read all the way through this document.
When you feel ready to begin using seq24, you may wish to use this outstanding tutorial.
Setting an instrument
To set a MIDI instrument, bring up a track editor window by right clicking a "track box" and selecting "Edit...". Select a MIDI device, or "output bus", and select a MIDI channel. There are 16 channels per MIDI device. Keep in mind that a channel can only play one instrument at a time. (So, you won't be able to play a piano sound on channel 5 and a flute sound on channel 5 at the same time) Also, channel 10 is always percussion. Next, select the "Event" button and select "Program Change". Add a program change event to the first tiny box underneath the keyboard roll by holding down the right mouse button and left clicking on it. Now, select the event box you just created with the left mouse button. You may now use the scroll wheel or right mouse button to change the value of the MIDI instrument. The instrument probably won't be set until the next time you "play" through that section of the track. You can read more about the standard set of MIDI instruments here.
seq24 has the ability to connect to other MIDI devices and software through the JACK software, including QSynth, amSynth, and ZynAddSubFX.