For those who don't know, Gunhild Carling is a multi-faceted performer who plays jazz trombone and trumpet, sings, plays bagpipes and recorder, plays 2 or 3 trumpets at once... etc.
Here is a video of her band doing Down by the Riverside using a euphonium as a bass. The young lady playing it sound very green at the instrument and at doing bass lines, but it's interesting to see her they anyway. I've seen several of Carling's videos and never saw the euphonium, so maybe this was a first-time experiment or some such thing.