You can sort of still feel and sense the attatck and the vestibular effect of the keys being played despite their tones being filtered out?
Example? I think you can answer your question by putting the sound you are hearing into audacity. Look at before and after. I suspect the low pass isn’t perfectly removing all high frequencies. Plus in a real piano there are low frequencies present from the mechanics of the wood keys and hammers.
Are you talking about something like Soothe or SplitEQ? There are certain spectral effects that can remove the tonal characteristics from a sound, leaving only the nontonal aspects. E.g. on a piano, you’d only hear the unpitched, percussive hammer and key sounds.
Here’s a FOSS alternative for Soothe. https://bedroomproducersblog.com/2024/03/03/nih-plug-spectral-compressor/