KöMaL 2025 K880

Eight three-legged dragons formed a choir. As we all know, a three-legged dragon can have one, three, seven, or nine heads. The three-headed ones are sopranos, the seven-headed ones are mezzos, the nine-headed ones are all altos, and the one-headed ones do not sing, they can only be choir leaders. The dragons have altogether twice as many heads as legs. How many heads could have sung each voice of the famous three-voice choral piece: "I wish I were a rosebud".