Which of the following musical bands is not a quartet?

And behind ABBA were the 10 or so session musicians who made up the band.

My few favourites came from Modern Talking all of which are listed in the description.

I thought Geronimo’s Cadillac was by a US singer . Can’t recall whether it was Michael Murphy or Martin Mull . Haven’t heard it for about 40 years

Aww....never heard of them! And I love 80's music 🤗