For those of you with iPhones / iPod Touches, I commend to you Paklsound, a music sequencer - see http://pakl.net/iphone/PaklSound1/. There is a video of it here http://www.youtube.com/watch?v=G4CGkC1TpME although I suspect that may be an older version based on the date and the functionality displayed - it now has 3 screens rather than 2, the high notes displayed in the video, the percussion demonstrated and bass. It costs 69p or thereabouts. Clearly this is a 'if you like that sort of thing that is the sort of thing you would like' deal, and it is limited to 32 notes - 2 screens of 16, though all notes of all 3 'screens' or whatever you want to call them can be polyphonic, but I think I have got my 69p of entertainment out of it.