In Mandarin Chinese, mai3~mai4 are a pair meaning "buy" and "sell", so I
suppose that distinction could percolate through a conlang. But I guess that
would be lexical tone, unless you treat pairs such as buy and sell as two sides
of an active-passive system.
If you want to hear what Ancient Greek, complete with pitch-accent system,
look up Stephen Daitz. He's made several recordings using reconstructed
phonology. Warning: it does _not_ sound like the dialogue of Socrates in my
head when I read a dialogue
Na'gifi Fasu'xa has a pitch-accent system.
I am ashamed to admit that