Tuba
Compensating valves

Some tubas have a compensating system to allow accurate tuning when using several valves in combination, simplifying fingering and removing the need to constantly adjust slide positions. The most popular of the automatic compensation systems was invented by Blaikley (Bevan, 1874) and was patented by Boosey (later, Boosey and Hawkes, which also, later still, produced Besson instruments). The patent on the system limited its application outside of Britain, and to this day, tubas with compensating valves are primarily popular in the United Kingdom and countries of the former British Empire.

The Blaikley design plumbs the instrument so that if the fourth valve is used, the air is sent back through a second set of branches in the first three valves to compensate for the combination of valves. This does have the disadvantage of making the instrument significantly more "stuffy" or resistant to air flow when compared to a non-compensating tuba. This is due to the need for the air to flow through the valves twice. It also makes the instrument heavier. But many prefer this approach to having additional valves – or to the manipulation of tuning slides while playing – to achieve improved intonation within an ensemble.

Most modern professional-grade euphoniums also now feature Blaikley-style compensating valves.
oulipo:avoid_letter[o], startend:quotation, combination:two_responses