Question about 1982 repeats

On some of the shows from 1982 there is the credit 'Musical Director Ronnie Hazelhurst'. For anyone who doesn't know who he is he wrote the theme tunes of some of the most famous sit-coms in British TV history like Last of the Summer Wine and Some Mother Do 'Ave Em. Does anyone know how he came to be working on the show when most acts do not need any backing?