upright piano vs forte-piano

upright piano and forte-piano both are nouns.

Word	Noun	Adjective	Verb	Adverb
upright piano	Yes	No	No	No
forte-piano	Yes	No	No	No

As nouns, forte-piano is a hypernym of upright piano; that is, forte-piano is a word with a broader meaning than upright piano:

upright piano: a piano with a vertical sounding board
forte-piano: a keyboard instrument that is played by depressing keys that cause hammers to strike tuned strings and produce sounds

Other hypernyms of upright piano include piano, pianoforte.

upright piano (noun)	forte-piano (noun)
a piano with a vertical sounding board	a keyboard instrument that is played by depressing keys that cause hammers to strike tuned strings and produce sounds