The singer (Dave "Doc" Robinson) does sound like the singer from Looking Glass (Elliot Lurie), the group that did Brandy.
In fact both bands have similar, but distinct (if that's possible) sound. One of the guys from King Harvest went on to found Orleans of "You're Still The One" fame. Yup, that was a Rhodes piano, you'll find it in similar groups such as Three Dog Night (which you really should check out) and Orleans.
Here's another: Blue Swede "Hooked on a feeling."