Is there a word or expression for a musical instrument which,
like a xylophone or a set of bells, has set pitches (fixed frequencies) that no one can change or adjust (except by some extraordinary measure like sandpapering the bars),
like a piano, has pitches that can be changed by a tuning professional but are set for the performer, and
like a violin, can give the performer any pitch he wanted in some range.
If you had these words you could ask a question like, 'Is a trumpet a piano-like or violin-like instrument,' or make a statement like, 'a guitar is somewhere between piano-like and violin-like.'
The word need not be an adjective.
I am not asking what would be a good word we can start using for these things. I am asking, if music theory, physics or any other discourse already has such words or expressions, what are they?
Please excuse my ignorance if, for instance, a xylophone can be easily tuned or a guitar is not meant to be violin-like at all.