1. I’ve repeated a short poem several times (and I’ve even embedded some in well-known songs in the public domain – like Pachelbel’s Canon).
2. I’ve written short songs. LOL – short poems – short songs!
3. I’ve combined poems with similar themes/moods.
4. I’ve repeated words and lines to lengthen a poem a bit.
5. I’ve even written my own lyrics to add to a poem.
There are other methods too:
6 .One reader said in comment yesterday, “another strategy, common in rock songs, is to simply add a minute or so of instrumental intro. Then you don't need so many words in a song!” – and I’ve done that with introductions and musical interludes in the middle of songs.
7. I’ve also taken lines or stanzas to create a “chorus” that repeats throughout the song (typically, songs are made up of “verses” followed by a “chorus,” often the part that contains the most memorable or catchy part of the song).
In the song I wrote pictured below, I combined two poems – AND – I borrowed some lines to create a chorus that repeats several times.