I worked up the Duelling Banjo and Kazoo routine when I got fed-up with being asked for duelling banjoes (usually by some bloke holding a guitar, expecting me to do all the work and him bum along for half of the applause). As it happens I do NOT play bluegrass banjo, so I did the flash bits on kazoo and the accompaniment was clawhammer style on the five-string.
I reckon a trombone would sound brilliant on the runs, especially with rip-snorting slurs and glissandoes.
By the way, Bullfrog. Where are you based. I recall a band of that name playing pubs around Bradford when I used to live there. Was that you, or is it a coincidence of names?
Quack!!!
Geoff the Duelling Duck!