Sky Ryders 1986 (Wizard of Oz show, second time) the hornline vocalized the opening chord of "Over the Rainbow".
During the Mellophone solo the horns gradually faded into playing the same notes on their horns so you didn't notice that they had done it unless you listen for it.
(They mayhave done it in 1985 too but they didn't make finals so I don't have a recording of that show)