You just can't have too many birthday songs, can you? This one is a charming and odd little tune. Very sparse and repetitive, yet quite interesting, it's memorable and fun to perform.
Parts 2 and 3 add background vocals, but the tune can absolutely be sung in unison. It works beautifully a cappella, as well. Isolated rehearsal tracks for parts 2 and 3, as well as an a cappella demonstration, are included with the kit. (from Music K-8, Vol. 19, No. 4)