Oh man, Morgan Griffiths is/was my all-time favorite for sweet sounding euphonium playing. I think he liked playing his Besson 966 the best if I recall. His playing of "Lament" on "Cry of the Celts" CD with the YBS Band is still one of my favorites. Also, "Macushla" on that CD. Can listen at link below. Just pick the track.
Cry of the Celts - Yorkshire Bldg Society Band
sorry, didn't mean to get OT.