Wagnern.

1938 Oxf. Compan. Music 963/2 What are sometimes heard to-day under the name of ‘Wagner Tubas’ represent a considerable modification of the [tenor, bass, and double-bass tubas].., so far as the tenor tuba and bass tuba are concerned, departing more from the French horn model as to bore, and approaching more to that of the saxhorn; they retain..the funnel-shaped mouthpiece of the horns.

1948 Penguin Music Mag. June 132 No one explained that the ‘Wagner tubas’..were assorted saxhorns, with cup-shaped and not funnel-shaped mouth~pieces.

1961 A. C. Baines Musical Instruments through Ages 315 Wagner tubas, ‘tuba’ here is really a misnomer, the proper name for these instruments being Wagner-Tuben... These Tuben, conceived by Wagner to bridge certain gaps in the brass tone, are made in two sizes, in B♭ and F, at the same pitches respectively as the B♭ and F horns and using the same part of the harmonic series. In bore they are midway between the horn and the saxhorn... They are fitted with four valves, the purpose of the fourth being to improve the intonation of the lower octave.

1965 Listener 3 June 837/3 A platoon of Wagner tubas.

1980 New Grove Dict. Music XX. 152/1 Wagner tuba, a special kind of tuba devised by Wagner for the Ring with the object of bridging the gap between the horns and trombones... The main body of the instrument is elliptical, like most German tenor horns, with the bell emerging from the top at a slightly oblique angle, while the lower end almost rests on the player's lap.