Poems that best fit with "traditional" art song (more on this adjective in a moment) tend to meet the following criteria:
- shorter poems, fewer lines
- more vowels, less consonants, especially "hard" sounding ones
- shorter words (the fewer syllables the better)
Shorter poems can be a good place to start thinking about as possible candidates for art song. In terms of consonants and syllables, the ones that have fewer on both counts would be a better fit.
The shorter the poem is, the easier for the composer
The longer the poem, the more the composer and the music must "chase" the words in order to complete the poem (unless the art song draws from an excerpt of the poem). The shorter the poem, the more the composer is able to play with it, expanding her/his palette (e.g. repetition).
Poets sometimes choose longer poems to submit so that composers have more to work with. While this choice makes some sense, it also runs into two issues: longer poems can be harder to arrange and composers may not want to excerpt the poem if it means “cutting up” a work of art. There's nothing wrong with having a longer poem so long as the poet feels okay with either having it excerpted or having the music chase the words (the latter is usually not ideal).
Shorter words and more vowels are easier and more beautiful for the singer
In terms of sound, vowels are more mellifluous to sing than consonants and multi-syllabic words lead to fewer possibilities from a compositional and singing perspective. The fewer the syllables, the easier it is for collaborators to play with them.
While vowel and consonant use might be interesting to think about in standard poetry, thinking about vowels and consonants is crucial for art song poetry. There is not usually a reason to pay special attention to vowels and consonants (e.g. in poetry workshops), which is why a poem that might be a good poem in one context may fit differently into art song.
A caveat about "traditional" art song
These are the features of a good, "traditional" art song poem. Yet these tips come with caveats: composers and performers can rightly pride themselves on being able to meet the demands of a challenging poem on these counts (i.e. one that is long, consonant-heavy, and/or polysyllabic). They can identify with wanting to meet the poem where it is rather than being handed a poem that is easy, so to speak. Some can believe that a poem is something that should be autonomous and static, like a bug preserved in amber.
Ultimately, we need to make informed decisions as poets as to what we believe we are offering collaborators: a poem that is a "good" art song poem or one that is more challenging to turn into art song. As poets, we set up pre-conditions for collaboration with our poems.
Let us know what you think in the comments below!