What I am about to write is off the top of my head and as much as I can remember from the facts. It’s certainly a close enough version of the truth to give you an idea. I would recommend that you dig around on the net should you require absolute accuracy with dates.
Robert Cohen, an ex-principle dancer from the Martha Graham company, with the financial support of Robin Howard, formed London Contemporary Dance Theatre School ( the PLACE) in 1966. They placed an advert in the Evening Standard, a London newspaper, looking for any pianist that might be interested in playing for a contemporary dance class (I believe they may even have advertised nationally). There was one single response by a woman called Judyth Knight who had previous experience in playing for church and arranging music for choirs. She attended the Graham studios, New York, to gain some knowledge of class playing and then continued to play and manage the accompanists at the PLACE for many years. Apparently, although I have never found them, she notated two books on how to play for a Graham Class and composed music for at least one choreography. I think its fair to say that any dance student, teacher or fellow accompanist that ever came across Judyth, was left with a lasting impression!
I should mention that a very important British company and school, Ballet Rambert, although founded in the 1920`s, started to change from classical repertoire to more contemporary choreographies in the 1960`s and they have always performed and work with live music. Many other companies and schools began to immerge from the 1970`s and this led to a need for more musicians who could play with an understanding for dance. There were ballet pianists who turned their hand to play for modern class and pianists, guitarists and percussionists were able to find work playing for a contemporary class.
I think the height of popular demand, as far as Contemporary Dance goes, was during the 80’s where companies were performing everywhere to full theatres. Nowadays, there are fewer supported companies but dance schools always have a contemporary dance programme and so there does remain work for an accompanist.
here is a clip of the late Judyth Knight playing for a class of very early dance technique
paul pavey 