What rhyme scheme (if any) is used in the event part of the Thomas and Beulah collection?

Rita Dove's poetry collection, Thomas and Beulah (published in 1986) tells the story of a married black couple in Akron, Ohio who are the poet's maternal grandparents. The collection includes forty-four poems, of which slightly more than half belong to Thomas (in the first part titled "The Mandolin") while the other half has Beulah as its speaker (titled, "Canary in Bloom"). "The Event" is the first poem of the first part. The rhyme scheme is free verse: unrhymed and without a specific meter.
The first several stanzas of the poem read:

Ever since they'd left the Tennessee ridgewith nothing to boast ofbut good looks and a mandolin,
The two Negroes leaningon the rail of a riverboatwere inseparable: Lem pluckedto Thomas' silver falsetto.But the night was hot and they were drunk.The spat where the wheelchurned mud and moonlight,they called to the tarantulasdown among the bananasto come out and dance.You're so fine and mighty; let's seewhat you can do, said Thomas, pointingto a tree capped island.Lem stripped, spoke easy: Them's chestnuts,I believe. Dove


Occasionally, Dove features a half-rhyme ("You're so fine and mighty; let's see"); however, there is really very little rhyme structure, and, while the poems have stanzas of equal length, there is no discernible meter (which necessitates a pattern of stressed syllables). What is interesting about this poem is the way that Dove locates her syntax within a stanza. Specifically, her sentences span different stanzas so that the reader is drawn into each recurring stanza. Using this syntactic approach, one could argue that Dove doesn't need a formal rhyme scheme.
Later in the poem Lem will die in the river, and Thomas will spend much of his life grieving (as demonstrated in his poetry) grieving.