A few years ago I was recruited to play in a 7 piece, 60s-80's rock band for 6 months. The band consisted of lead guitar, rhythm guitar, bass, drums, two non-playing vocalists and me playing an arranger. My role was to be any other instrument they needed. Strings, horns, piano, organ, etc. Never played a style or rhythm. It was fun for the better part of the 6 months, but was glad to get back to being a single. In short re: Chas's question....the arranger was perfect for the job. Nothing else required.
Eddie