TI as a saturated transient shaper (sounds a bit like an overdriven compressor):
Setup an input patch (ROM A-125), with input follower active. basically gives you an envelope of the incoming sound level.
Set filter mode to analogue, select filter combo of choice.
Setup a slot in the mod matrix sourced from filter env, with desitinations as:
Patch volume - -30 to -60.
Osc Volume - try +5, to +15 for light overdrive style sat
Now play with attack/decay knobs - these effectively set your 'compressor' attack/release. Try At=25, De=85, Sus=110 as a starting point for processing pianos, also tweak the mod -ve send amount to patch vol
Abuse filters and other fx to taste - if abusing a piano - add loads of reverb, long decay, no damping and tweak the eq
