From Wiktionary, the free dictionary
singable (comparative more singable, superlative most singable)
- Capable of being sung.
1981 February 14, Maida Tilchen, “Alix Living With Contradictions”, in Gay Community News, volume 8, number 29, page 18:
Alix has a consistent style but she's a fantastic writer of melodies, and every tune stands on its own. What she does best is to take highly verbal, lyric-centered songs and make them musical, catchy, and singable.
capable of being sung