A group of valved brass instruments, soprano to contrabass, invented by the Parisian maker François Sudre and patented in Paris on 18 February 1892. Although the principal length of tubing was folded back on itself as in the Ophicleide, and the valve assemblies bracketed out at one side, the proportions of the air column and acoustic characteristics were similar to those of the Saxhorn.
The unique feature of sudrophones was a device which permitted the player to modify the tone at will, and it was even claimed that reed or string timbre could be simulated. A brass cylinder attached to the bell communicated with both the air column and the external air through two opposed slots. An inner cylinder carried an adjustable stretched membrane of silk. By turning the inner cylinder to the left or right, the slot in the bell was either closed off or occupied by the membrane, whose vibrations modified the timbre after the principle of the Eunuch-flute. (See also Mirliton.)
PHILIP BATE