The orDrumbox is a free drum machine software,
designed to be as creative as possible with unusual features : auto-composition,
polyrythmes, unusual arpeggiator, automatic sounds/track matching , custom softsynths, lowfi rendering, etc.
This tools can compose bass line and complete songs using included drum kits with the audio sequencer functions.
How to write your very basic pattern from scratch (in 30 seconds)
Test online : It's a light version of the orDrumbox as a java applet.