- Clifford Bevan
A device invented by Wilhelm Wieprecht (Prussian patent 10,803 of 27 Oct 1838) allowing valved brass instruments to play portamento. The principle was based on the use of a spring-loaded tuning slide which allowed the air column to be lengthened, as it is in the trombone, with a consequent gradual lowering of pitch. So far as is known no instrument has ever incorporated the invention. The requirement for valved instruments to play glissandos, not uncommon in the works of recent composers, is met by half-depressing the valves and controlling the speed of vibration of the air column by means of the embouchure....