A poem by Minamoto Unkai 源雲界, Meiji shakuhachi guy and sometime Hokkaido resident:

Dust swept away by little waves
And fish caught gathered in their schools: Shirahama
A yaysama's mournful strains on northern seas
A tonkori-mukkuri break: uppopo-po-po.

A yaysama (or yayshama) is literally a song of "one's side", a song about the self. Apparently it is possible to sing someone else's yaysama; here's Toko Emi singing one about her grandmother's grandmother.

Tonkori and mukkuri are instruments, strongly identified with Ainu culture as they have no counterpart in Japanese music. On the other hand, the word I have translated "break," ai no te, is used in Japanese art music. It refers to a short instrumental interlude, usually connecting two lines of the lyric. The unseen Ainu musicians of the poem are implicitly put on the same level as the shamisen-and-koto musicians down south.

Uppopo-po-po is harder to figure out. Upopo is a word for a type of song, apparently a canon sung by people (usually women) sitting in a circle. It doesn't seem to have much overlap with yaysama. On the other hand the addition of the extra po-po suggests that maybe Unkai is using it for a sort of semi-onomatopoeic effect: the sound of Ainu music, if you will.