2b1fa9dc_Clarinet__effects__4
[0] harmonic [1] produced by fingering a fundamental low note, then picking out partials using venting, register keys or octave holes [2] o - over the notehead. (It is probably a good idea to include a note explaining whether the notehead is the sounding or fingered pitch) [3] harmonics [4] 
Very rare and fairly ineffective on the clarinet.
Clarinet: effects
4