I'd always thought it was an autoharp, but that was as a post-event deduction rather than a clearly remembered observation! Sorry if I'm wrong. Re the Radio Ballads, we have a confusion between Charles Chilton and Charles Parker. Chilton is not mentioned in the index of Maccoll's autobiogray. Parker gets 30+ pages. (Also, I have somewhere several additional pages Maccoll sent me about the genesis of the Radio Ballads, for which some [BBC] people give Parker all the credit.)

Ewan McVicar