Sets of reedpipes with single reeds
The air itself is the vibrator in the primary sense. The standing waves are significantly confined within the instrument itself. In each pipe in the set of two or more, the column of air is made to vibrate by the intermittent access of an air stream produced by means of a [single] 'reed' consisting of a lamella which periodically opens and closes an aperture, controlling the flow of air. The instrument is tuned by altering the lengths of the air columns. With wind-cap.
Sets of wind-cap reedpipes with single reeds
Hornbostel - Sachs