The basic note
The basic note of the didgeridoo is a low tone with a frequency that
corresponds to the low register of the pianoforte - the register of
bass instruments like the double bass and the tuba.
More precisely, the note of the didgeridoo is usually between about 60
and 90 Hz, or more formally between the musical notes, C2 and F#2.
For another comparison, the male voice has a standard frequency range of
100 Hz to 300 Hz, or more formally from G2 to D4.
We should note that the human hear does not perceive a note below a
frequency of 20Hz.
This note is produced by holding the lips together and blowing to create a
vibration of the lips. The resting position of this vibration is
with the lips pressed together lightly. This note is produced with the tongue
held more or less in its rest position. The cheeks should not inflate
when playing this note.