I tried using Ableton for a bit, but it was quite involved. Then I found
Quartz Audio Master, which is free.
If you want, it just shows a grid of notes, which is all I needed. It is a bit more limited than Ableton in terms of managing and triggering patterns however.
A useful tip - get yourself the
MIDIOX utility and the MIDI Yoke driver if you will do this stuff.
Get Resolume and your sequencer to listen on a virtual port for input, not the real devices. Then you can wire the MIDI devices into resolume or the sequencer as you choose, without making any configuration changes.