How fast was the response back in the days when Roland did have a momentary function for bass inversion?

I would have thought that with the note ‘jumps’ if you change from inversion on to off (like you get if you input a chord fractionally late and the current chord starts then instantly jumps to the new chord) would make a very short duration press into inverted and back rather unmusical. One would have thought that if you need an inversion or slash chord, you would need to hold the pedal down for the duration of the chord?

So the issue of switch ‘bounce’ is rather moot, isn’t it? I’m not talking about a switch that engages bass inversion on on press and back to normal on the second… I’m talking about a system that is normally regular chords and only goes to inversions on the pedal down, and immediately back on release… but this isn’t something you’d quickly hit and release like a sustain. And I don’t think it is a function of the switch itself that is the reason for a certain window of recognition for the function, but more an OS thing. It doesn’t make musical sense for ultra rapid changes of bass inv. on/off, and it would certainly tax the style engine.

It sounds like this can be achieved simply ganging two cheap pedals of opposite polarity together and using two different inputs…. You might get some unpredictable results if you press and release very quickly, but I don’t see how you wouldn’t no matter what system was used.

As to the Part Mute functions, I believe only the D-Beam can achieve these…. It has always frustrated me that Roland (and every other manufacturer, if the truth be told) seem to decide that a full selection of functions for ALL possible control inputs is too complicated for us poor dumb arranger players!

But the Part on/off is a binary function, not really a momentary, so it lends itself well to the D-beam. Build a little hood to shade it like you would to read the main displays outdoors, you should be good to go…

Diki I never actually played an FP-50 or FP-80. But it's apparent from the owner's manual that these style pianos have Bass Inv implemented as a momentary function, optionally assignable to one of the three piano pedals. So it certainly can be done and has been done with professional results.

The FP-50/80 are contemporary with the BK-series and may share some of the OS. The BK acknowledges the status of Bass Inv at the same time it recognizes the chord. If you do anything with the pedal after that, it doesn't have any effect until you play the next chord. There are no weird portamento effects, and it doesn't sound like the bass player swallowed a clam. It works seamlessly and as expected.

Depending on the mix of chords in the song, turning bass inv on and off in real time can save big "jumps" of the left hand, or wide finger spans such as would needed to play Cmaj7 with root bass, etc.

Yamaha knows this too. That's part of the justification for developing their flagship "AI Fingered" mode, which gives an on-bass chord for two-note fingering, and the root bass when three or more notes are played. This approach introdcues its own well-known set of problems. For most of the songs I play, Roland's chord intelligence -- with momentary bass inversion controlled by a foot pedal -- is an easier and more consistent approach. I offer the details here so that others may consider it, and adopt it for themselves.

In that case, I’d probably not worry about switch bounce, depending on whether a change of Performance messes with the chord ‘hold’ until the next chord. Mind you, from the front panel, changing inversion seems to be not dependent on another chord coming in at all. But yes, it does seem to wait for the next NOTE in the bassline before it changes.

I rather sidestep the whole issue myself by generally playing a full keyboard part for the first verse and chorus in Pianist2 mode, which naturally gives me the correct inversions (while I sing the head) and use the chord sequencer to play the solo sections so I don’t have to input any chords at all or worry about their inversions during solos or improvisations. Even the most basic two handed chords can drive the arranger while keeping the bass inversion correct.

But I still think the two opposite polarity ganged pedals should work to go momentarily from one Performance to the next and back. Have you tried it yet? There are plenty of tablet style footswitches that are switcheable polarity and quite cheap.
https://www.sweetwater.com/store/detail/KSP20--on-stage-stands-ksp20-keyboard-sustain-pedal for instance. Just glue or Velcro something hard across the pair to make them both work at the same time, and build an FC7 DIN plug to 1/4” female jacks converter….

Push comes to shove and you end up not liking the system, you can always retask them to other useful FC7 functions like Leslie fast/slow or MFX on/off etc..

The Performance can store far more than OTS can, I still think it’s your better bet and will dramatically reduce your having to navigate around to call up custom styles.