Hydrogen is a really cool drum machine for linux. This Ubuntu application allows you to create professional tracks by programming drum patterns. It is multitrack enabled, meaning that you can add up to 64 tracks worth of music data to your beat. You can use 32 instrument tracks, and they are multilayered (meaning that there can be up to 16 samples for each instrument).
Generally, drum machines sound a little cold and really different from the way a real person would play the drums. Hyrdogen gets around that by adding in unique human velocity, human time, pitch, and swing settings, giving the song and drum track a much warmer feel. With that, you can make the perfect song to export to Audacious or Amarok.
Hydrogen is included in the official repos, so you can install it from Synaptic, by clicking this link in Firefox, or by entering the following command:
sudo apt-get install hydrogen
If you want to get the latest Ubuntu Applications, be sure to subscribe to The Daily Ubuntu feed.