On American Bandstand in 1981, on this video at 2:15, Carl talks about Myrna Smith recording songwriting sessions (demos, presumably?) on her "little cassette machine"... I'm guessing this means that somewhere, there are songwriting demos of Carl's solo songs, that were apparently recorded at Myrna's house.
https://www.youtube.com/watch?v=AzfYSrFpiUoCurious if any archivists have tried to unearth these tapes that Carl talks about?
I'd also tend to think there would be similar homemade demo tapes for lots and lots of other BB-related material. It would tend to seem logical.
Side note: Myrna is definitely one of the very few female songwriting collaborators that The BBs have ever written songs with. How many others are there? I know Brian cowrote some material with The Honeys, and Alexandra Morgan had some input (although how much is debatable) on songs such as In My Car.