Wessex tuba -- what does the trigger do?
Community band has started up after a year's layoff, and the tube player who sits next to me has inherited another [former] player's Wessex tuba. It's a rotary 4-valve, but it also has a trigger-operated rotary valve for the right thumb. The player figured out that it seems to add a minor third's worth of tubing to the sounding length, but neither he nor I can figure out how it should be used. If an expert could fill me in, I'll pass the word on to him. Thanks in advance.
David Bjornstad
1923 Conn New Wonder 86I, Bach 6 1/2 AL
2018 Wessex EP100 Dolce, Denis Wick 4ABL
2013 Jinbao JBEP-1111L, Denis Wick 4AM
2015 Jinbao JBBR-1240, Denis Wick clone mouthpiece of unknown designation
Cullman (AL) Community Band (Euph Section Leader)
Brass Band of Huntsville (2nd Bari)