I was trying to find some sequencing software to play bass & drum parts whilst I did some guitar practice. I initially tried Quartz but found the process of adding notes to be painful (may have been a mouse issue, but the software would not recognise a mouse-drag to play a longer note).
I also tried Anvil. I must admit that I almost didn't since the installer had to be run as Administrator. The free version of the software has its limitations, but was sufficient for my needs. Putting the music on the piano roll was pretty quick and easy. Adding a drum pattern was trivial thanks to the inclusion of looping capability.