Hi
Can't help I'm afraid but just wanted to say I'm having exactly the same problem trying to recover some important work files and getting the same error message. I have contacted the Recuva support centre but have received no reply. Not happy that I have paid for a data recovery service that doesn't even start to try to recover the data and that the support advertised seems to be non existent.
Sorry to hear about your husband - I hope you get the music back.