Question

what is a musical piece in which one solo instrument such as a piano or violin is accompanied by an orchestra

Answer 1

I believe its called a concerto

Answer 2

the trios can have very varied instrumental combinations, although the most widespread are:

Trio of string: violin, viola, cello.

Trio with piano: violin, cello, piano.

Trio of clarinet, violin and piano: clarinet, violin, piano.

Trio of clarinet, viola and piano: clarinet, viola, piano.

Clarinet, violoncello and piano trio: clarinet, cello, piano.