De or het triosonate?

The correct Dutch article is:

de triosonate

Rule Words ending in -te: usually de. See the rule

How to use triosonate

the triosonatede triosonate
this triosonatedeze triosonate
that triosonatedie triosonate
our triosonateonze triosonate
your triosonatejouw triosonate
every triosonateelke triosonate
which triosonate?welke triosonate?
a big triosonate / the big triosonateeen grote triosonate, de grote triosonate