My "oldest living" adult amateur student is an extraordinary world-class scientist, mindful of the vast chasm that separates her work from what she once referred to as "the music part" of music. Needless to say, she is deeply insightful into the workings of the elements in music as in science.
Today, working on her Haydn D major sonata, the issue arose of note values in relation to improvisation, lee-way, variability. Without a strong element of those free elements the note values in Haydn have the power to kill the music.
It is ironic that Haydn's sonatas are as free-form as they are while jazz improvisations are based on what seem to me, in contrast, to be quite tight structures. Of course Haydn was faced with a real dilemma: how to evoke orchestral sounds from a newly invented keyboard instrument whose sound was unlike any previously possible from black and white keys played by two hands with the addition of foot or knee-controlled dampers.
It would have been accepted harpsichord technique to sustain some tones beyond their notated value in order to foster what little sympathetic vibration was possible with harpsichords.
Modern pianists are taught to obey the printed text as if it were the music; sustaining a note beyond its prescribed value is a no-no. But it all depends on the function of the note. Sometimes eighth notes have to function as quarters in disguise, sometimes as tied whole notes in disguise. At other times it is clear that they are eighths and must be released promptly. How do I know?
I pay a lot of attention when I listen whether to amateurs or professionals. Listening has taught me the power of the release and the corresponding power of the urge to sustain.