The bawu typically has a range of an eleventh: on an instrument in "G" (according to Chinese custom the note with three upper finger holes down) this range is from B to E. The range is often misreported as a ninth, omitting two underblown notes. Instruments with mechanical keys are available (usually not in natural bamboo whose irregular shape would complicate construction), which expands the range upwards, or upwards and downwards a few notes. For a diatonic scale, the lower two notes are in the fundamental mode of the reed, and the rest of the range is overblown, exciting the vibratory mode of the resonating pipe. The lowest scale degree, and the lowest overblown note are a minor third apart and fingered the same way; this unusually narrow overblowing behavior suggests the instrument has some irregular overtones outside of the standard harmonic series.

The lowest part of the bawu range is very rich in upper harmonics, the lowest of which have amplitudes almost equivalent to that of the fundamental frequency. This results in a rather buzzing timbre that is vaguely harmonica-like and in terms of sound spectrum very typical of free-reed instruments. As successively higher notes are fingered, the upper harmonics are gradually extinguished; the even harmonics are disproportionately affected, resulting in an odd-harmonic-dominated sound in the upper range similar to the clarinet both in terms of spectrum characteristics and subjective tone color. The underblown notes are close to the fundamental frequency of the reed, but the overblown notes are slightly sharp of the fundamental frequency of the air column, suggesting relatively complex acoustics.