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5th is a bit larger then 1st. To be used with 4th. Use 4th+5th instead of 4th+1st to play a low Bb, for exemple.
6th is a bit larger then 2nd. To be used with 4th. Use 4th+6th instead of 4th+2nd to play a low B natural, for exemple.

5th and 6th compensate for the lenght of the instrument when 4th valve is pressed. This way you dont have to push and pull slides while you are playing.

Sorry for my english...

einahpets wrote:I know the bass can never sound like the contra but does this help it come close?

The extra valves are simply to improve intonation, particularly in the low register. It will still sound like an F tuba!

Go to "for sale" silver 188. then google Burning River Brass and listen to some of the youtube clips, then contact Matthew and get the whole package (inc flight case) shipped out. (Maybe get some cds to study as well. Then, except for telling us all what a great horn you got at a good price, get in that practice room and forget about Tubenet for a while.