As the MicroBrute is monophonic - meaning it can only play one note at a time - I am not sure there would be much point in trying to play a separate part on the keyboard as the synth engine would already be running at full capacity. When the MicroBrute's internal sequencer is playing, the keyboard can be used to change the key of the sequence. If you're running it from an external sequencer, playing the keyboard would disrupt the sequence - sometimes in a good way such as adding occasional variations, but sometimes in a bad way that won't sound right at all. It's one of those things you can try, though, without anything breaking. :-)