My husband started his pro career singing in a dancehall in an orchestra in the late 60s. It's what brought us to Yorkshire, as the band were contracted to Top Rank. Sadly within a couple of years they were being replaced by DJs, much cheaper!
He was fortunate in working with a couple of local big bands, as well as the Memphis Belle Orchestra who worked in theatres, mainly in the South, but also were in demand for occasions like VE celebrations. His bread and butter work was in social clubs, but that could be a hard slog depending on the resident backing! Some were fabulous musicians, others....
Big band/swing is still his preferred musical genre.