Inferring saxophone response from input impedance measurements

It is generally expected that some aspects of a wind instrument’s response or playability can be inferred from its input impedance. As a test case, we consider the lowest notes on a curved soprano saxophone, which are typically difficult to play cleanly at medium or soft dynamic levels. It has been found that dropping a wine cork into the U-shaped elbow of this saxophone improves the response of the low notes, without causing any obvious problems with higher-range notes. Input impedance measurements were made on the soprano saxophone, with and without the cork in the instrument. The presence of a cork in the elbow slightly lowers the first impedance peak frequency and magnitude by 2–5 Hz and 2–3 dB, respectively, for the lowest three notes, though the next few higher impedance peak frequencies are either increased or not affected. The presence of the cork significantly increases the magnitudes of a broad range of impedance peaks between 4–7 kHz, which might suggest higher mode influence for note stability. Several different impedance metrics are explored, including inharmonicity and average harmonic power, to investigate whether the differences with and without the wine cork can be linked to quantifiable aspects of the measured input impedance.