|Acoustics of the saxophone
Bb tenor saxophone
Notes are the written pitch.
At frequencies below about 1 kHz, this curve looks rather like that for A#3, B3, C4 or C#4, but raised in frequency because the tube is effectively shorter because of the three open tone holes (see tone holes). At higher frequencies, however, the waves propagate past the open tone holes with greater ease, and the situation is more complicated. See the discussion in cut-off frequency. However, the 1 kHz cutoff means that there are only three strong peaks, so only three notes that one can 'bugle' with this fingering. The first peak can be reduced in magnitude and shifted in frequency using a register hole (operated by the octave key). See D5.
This note is, acoustically at least, a cross fingering: there is a key closed below the first open key, as the schematic inset shows. Because of the large size of the tone holes, cross fingerings have little effect at low frequency.
For general comments about the first register, see A#3. Compare with the impedance spectrum for a soprano sax on written D4: same fingering but sounding one octave higher.
In the sound spectra for the low notes, we can notice a sudden increase in the negative slope of the spectral envelope that occurs close to the cut-off frequency of about 800 Hz. For general comments about the sound spectra of the first register, see A#3, which is the first note of that register.
Sound spectrum of a Bb tenor saxophone played using fingering for D4.
For more explanation, see Introduction to saxophone acoustics.
You can hear D4 played.