Leopards from the Sea
Its entry in the Radiophonic Database has the notes:
Reel returned from Delia Derbyshire. TMS (Television Music Studio) tape dated 2/5/71 Sound Supervisor Adrian Stocks T/G Operator Ray Williams Box marked "Reel 1 of 2", title "Leopards from the Sea". Idented orchestral recordings.
where "TMS (Television Music Studio)" seems to be the BBC Television Music Studio, Shepherds Bush, London, producing "title and incidental music for television programmes".
Its tape's catalogue entry is dated December 1970, so the 2nd May 1971 might be the episode's broadcast date. Unfortunately, the records of Chronicle episode titles for 1971 are very partial and do not include this episode.