Whenever Dennis played his horn is sounded easy and effortless. It had an extraordinary lyrical beauty and was always incredibly musical. He was a very sensitive player who listened very carefully to the other players and blended in with them. At first he played a French instrument, a Raoux piston-valve horn, similar to that used by his father. This type of instrument has a lovely smooth tone, but was less powerful than the German-made instruments which had become popular since the 1920s. In 1951 he changed to single B instrument made by Alexander, which was not quite as wide as the usual German instruments, still keeping the lighter sound of French horns.