The Bolland brothers are famous for their work with Austrian singer Falco, and as writers of the song "In The Army Now", a hit for Status Quo. In the 1980's, the Bolland brothers hired Johan for quite a few of their projects. They produced dozens of singles and albums, and often under nicknames. And it is even more difficult to find out on which record Johan played, as he was not always credited properly...
In the 1990's, Johan had his own band, called Doreen. They released a CD in 1994 ("It's Got To Be Love"), on which Johan played guitar and drums (!), and co-wrote 9 songs.
Some other projects:
Frederic Fly and the Flies: Stop And Go/Flies Of the Universe (single, 1982). Johan plays guitar on this single, which was written by 'Songstone and Hammerstone', which in fact were -if memory serves me well- the Bolland Brothers.
Johan Doornenbal: Communion (CD, 2003). Singer-songwriter Johan Doornenbal was a big fan of Kayak. He asked Johan Slager and Max Werner to help him out on his album, and they did; Johan Slager played keyboards and additional guitar. Max Werner played drums, percussion, sax, clarinet and keyboards, and sang backing vocals. The album was produced, engineered and re-arranged by Max Werner and Johan Slager.
Johan played on 2 albums by Circus Custers, a Dutch duo that also scored some hits. Johan played on their LP "Romantisch Verbitterd" (1983, not on CD) and on their CD "Kop In De Wind" (1989), which also features Ton Scherpenzeel. Most Circus Custers songs can be found on their various Best Of-CD's.
To be continued...