Japp joined May Fisher, a Llanelli-based band, just before it was taken up by a London rock and pop music agency – through a friend who went on to establish 3PR – and sent on an extended and successful tour of Yugoslavia under a new name: Thank You.
These were never released due to apparent difficulties in finding a vocal style from the band's two singers.
Japp had, however, made a strong impression on Marmalade and was invited to join the group to replace Hugh Nicolson.
He toured extensively with the band but no recordings made during his tenure achieved chart status.
He also wrote/co-wrote songs for such artists as Paul Stanley, Kiss and The Babys, and worked with other musicians such as Matthew Fisher and John Waite.