(BBC musical series, 1981)

Episode 1: At Home Chris Hough notes a “short series of musical playlets by Peter Skellern, one of which featured a Leyland Titan PD3/East Lancs of Leicester City Transport as an integral part of the plot which concerned a brass band going to a concert and I think losing an instrument from the rear platform.”
The bus in question is Leicester 21 (LJF21F), a 1967 Leyland Titan PD3A/12 bodied by East Lancs: