All problems in computer science can be solved by another level of indirection
I've been playing piano since I was about 11.
Not continuously, of course - my fingers would have fallen off a long time ago! In fact I've barely touched one for a decade.
I'm really more of a synth player - and I've never been a great performer - my interest lay more in composition anyway (some old pieces of mine over on soundcloud.com/phil_nash). But I appreciate a good piano action on a synth keyboard. I chose my Ensoniq TS-12 synth as it had one of the better piano actions (and piano sounds) when I bought it in the mid 90s.
But something happened in 2002 that changed the way I thought about it. I was trying to get back into playing again after a few dry years. I'd just bought a MOTU 828 (effectively a very low-latency external sound card) and a copy of Steinberg's "The Grand". The Grand was a VST instrument that was one of the first to use high definition, full decay, samples of every key on the piano at multiple velocities. That was amazing enough. But then it could perform addition processing - to apply the sympathetic resonance of the open piano strings when the sustain pedal is down, for example, or add in the sounds of the felt and hammers themselves. The result was a breathtaking leap forward in authenticity in digital piano sound.
There was only one problem. At the time the computer processing power, as well as disk IO, was limited enough that it didn't take much layering to push the boundaries. This resulted in note-stealing (where notes deemed least audible are culled, freeing up processing power for those more to the fore), freezes or even crashes. One option to counter this was to reduce the complexity of the instruments. Turning off features such as open string resonance - or using a simpler version of the instrument (e.g. my keyboard's built-in piano sample).
In theory that was an acceptable trade-off as it only really affected live playback and recording. The finished mix could be rendered in non-real-time, including all those CPU-intensive features in the final recording.
That's when I realised something quite surprising. When I played the full-featured version of The Grand I found I played differently to when I was playing the TS-12's on-board piano sound.
Even more surprising was that even playing a simplified Grand was noticeably different to playing the fully-enabled version!
And when I say I played differently the difference really was stark! The more authentic the piano sound, the more my fingers flowed across the keys. I was more accurate, more musical, and felt more connected with the music. Remember this was using the same physical keyboard with, essentially, the same instrument.
Audibly, the difference between a no-holds-barred Grand and one with the extra processing disabled, was very subtle - especially during normal playing. If you played a chord and let it ring you could hear the harmonics "shimmer" with the processing enabled. But I wouldn't consciously notice that while playing in general.
And yet I was quite clearly picking up on it and behaving differently as a result of it. Why?
Obviously all of that extra disk IO and processing was there to make the sound more authentic. To more closely mimic the nuances of the real world instrument. That's all intended to trick the listener's brain into thinking it is the real world instrument. But the player is a listener too. And the player, even one as unaccomplished as I, has a different interaction experience with a real instrument than an artificial one.
This has been quite a long anecdote to make one point: that small, barely perceptible, differences may have a huge impact on our experience - although not necessarily in ways we are consciously aware of. This seems especially true when applied to the way we interact with digital interfaces - whether that be a synth keyboard pretending to be a piano, or a touch screen pretending to be, say, a piece of paper. The details matter. We are participating in a fragile sensual suspension of disbelief. The tiniest crack that betrays the deception brings the whole thing down.
And we're only just at the beginning of a revolution in interaction metaphor.