Sunday Night At The Trocadero: 1937
Connie (later Connee) Boswell heard of the Brian Sisters from an acquaintance in their apartment block and realized that they had the same sort of 'togetherness' and musical competence as had her own vocal trio, The Boswell Sisters. Indeed, some of the Brian Sisters' songs learned from the radio earlier were those performed by The Boswell Sisters, although their singing style was different.

Connie was so impressed that she arranged for a short (20 minute) film to be made which showcased the Brian Sisters. The plot seeks to show that persistence alone is insufficient and that talent such as exhibited by the Brian Sisters would win through in its own right.
The Brian Sisters pretend to be unable to start singing - something from which they didn't suffer in reality! It was the speaking parts that they found difficult.
When you watch this film, you will see very clearly that pretending to freeze and fail was far harder for the girls than to get on and sing!
The sound-track is not in good condition, and the girls' speech in the foyer and dressing-room is unclear - please say if you need a transcription here. The singing is properly restored though.
They sang There's Always A Happy Ending with interesting slight individual variations that Connie made no attempt to change.
Only by listening carefully (or being told in advance) is it apparent that the band stops playing while the girls end the song with their variation – it differed from the printed band parts. There is only an occasional piano chord. Their voices carry it through strongly and faultlessly. When the girls have finished singing, the pianist plays a final chord and the band plays out the film.
This is a really super example of the girls' talent! Betty was 13, Doris 10 or 11 and Gwen 9. They sing with amazing precision and perfectly in tune. No wonder Connie loved them!
Sunday Night At The Trocadero is included as an 'extra' on the DVD The Marx Brothers - A Night At The Opera. If you look carefully at the patrons, you will see one of the Marx Brothers…
Connie was so impressed by the girls that she arranged for her Brother-in-Law, Sol Leedy, to be a professional manager for them for a while, relieving their mother of the chore at which she struggled but persevered.
Perhaps Connie helped the girls in many other ways, maybe even underwriting their school fees, without the girls being aware of it?