A register hole suppresses unwanted modes by sitting at their pressure antinode

Evidence

Overblowing is supported in instruments such as the recorder by opening a small “register” or “vent” hole, which is positioned such that it is at the pressure antinode for unwanted modes, and these modes will be suppressed. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1191

Once an octave and a fifth above the bottom note has been reached, the flue can be overblown to the third mode (an octave and a fifth above the first mode), and the fingering can be started again to ascend higher. The fourth mode is available at the start of the third octave, and so on. Overblowing is supported in instruments such as the recorder by opening a small “register” or “vent” hole, which is positioned such that it is at the pressure antinode for unwanted modes, and these modes will be suppressed. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1191

Categorization

• DEFINE: Gives the physical principle behind register/vent holes in woodwinds.
• corroborated: 4 independent passages support this claim — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1191
• XREF: connects to: Striking a membrane at a nodal line silences that mode entirely; Register holes force a jump to a higher mode by removing harmonic support.; Register holes exploit mode geometry to suppress one mode while sparing others. (+4 more)

Broader Connections

• A register hole kills one resonance while sparing another. #expands (0.95)
• Tone-hole fingering requires modes to keep constant frequency ratios as holes open #expands (0.80)
• Multiple open holes jointly shift the effective pressure node #expands (0.75)
• Pressure nodes and antinodes structure inside standing waves have complementary velocity counterparts #expands (0.72)