A Dictionary of Music and Musicians/Tuba (organ stop)
TUBA, TUBA MIRABILIS, or TUBA MAJOR, TROMBA, OPHICLEIDE, are names given to a high-pressure reed-stop of 8 ft. pitch on an organ. In some instruments, especially if there are only three manuals, such high-pressure reeds are connected with the Great Organ manual; but inasmuch as the pipes are of necessity placed on a separate soundboard supplied by a different bellows to that which supplies the ordinary flue-work, high-pressure reeds are more often found on the fourth or Solo Organ. The pipes of the Tuba are sometimes arranged in a horizontal position, but whether arranged horizontally or vertically, they are, as a rule, placed high up in the framework of the instrument. The wind-pressure of a Tuba, as measured by an ordinary wind-gauge, varies considerably; in some cases it does not exceed 7 inches, but in St. Paul's Cathedral the pressure reaches 17½ inches, and in the Albert Hall 23 inches or more. The pipes are of 'large scale,' and the tongues of the reeds are, of course, thicker than in the common Trumpet-stop. The Tuba is not solely used as a Solo stop; on large instruments, when coupled to the full Great Organ, it produces a most brilliant effect.
[ J. S. ]