Is possible to make the patch which make long sound based on short sound playing on piano (to make modifications of timbre and colour of lenghtened sound)? I mean for example the situation like this:

keystroke - this part of sound is elongated - end of sound

Thanks for all help.

Generally if you can define the 'sustain' portion of any sound, you can loop it or shorten it to make the note any desired length. ADSR stuff.

o, and by the way, ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn

Take a look at tabosc4~

It lets you do wavetable synthesis.

one technique is using an infinite reverb time to "freeze" a sound, then you can process it however you like

i think you can also use a phase vocoder to capture and freeze sounds, though i never tried it myself..

I`ll try all of this. Thanks.