Here's something that you may like. It's Beethoven's Piano Concero No. 3 and the Andante favori in glorious SQ quadraphonic, performed by Sviatoslav Richter on the piano, and Riccardo Muti conducting the Philharmonia Orchestra. This record was released on EMI/His Master's Voice in 1978, catalogue number ASD 3543.
If you're new to the SQ (Stereo Quadraphonic) quadraphonic matrix encoding process, check out this article on Wikipedia.