Click on any of the pictures to get really big versions of each.
I have recorded the sound of my tenor drone with varying lengths of the slide. 1950’s Henderson tenor drone, Selbie drone reed. Limits of this study are the resolution of the FFT analysis produced by Audacity using the Hanning window. Below is a graph of the pitch of the tenor drone from the FFT analysis and Audacity “change pitch” function. Agreement is okay/good.
Below are 3 graphs of the FFT analysis. The numbers on the right are how long the exposed tenor drone slide is measured in millimeters, mm. The note (in the bagpipe convention) is given over the lowest pitched tenor drone (longest exposed tenor slide – a yellow/brown colored line). The 2 longest exposed tenor slide recordings have an ‘h’ next to them indicating that hemp is exposed. Note that at E*, the harmonic spectra overlap, looking at spectra beyond the 3rd graph will give you a headache! All the spectra are normalized in such a way that the fundamental has a value of 1 dB. This is because it is ‘impossible’ to ensure that each recording captures the same volume from the drone for each different slide length. This is the only way to draw any conclusions from the changes in amplitudes of the harmonic spectra that accompany changes in tenor drone slide length (proportional to the length of the tuning chamber).
The left-most ‘A’ on the top graph below is the fundamental of the tenor drone.
Remember, dB is a logarithmic scale!
Amended May 5, 2011:
I also tried this on a Naill tenor drone with a Wygent reed and got the same results (it’s not normalized but the effect is easily visible):
The best summary of drone sounds I’ve ever heard (in words/type) was given by Shawn Husk in this thread on the bobdunsire.com forum:
Henderson type – generally a big sounding pipe; big bold bass, bright ringing tenors – the two sounds do not blend seamlessly but are typically stand alone, although they do compliment each other well. Slightly to mostly a bass dominant sound.
Robertson type – another big sounding pipe; this is very much like the Henderson type in every way save for the bass is less dominant and the bass and tenors blend a bit more seamlessly.
Lawrie type – big sounding pipe; very warm round bass sound, tenors are mild and very integrated. Overall a seamless bass dominant sound.
Naill type – generally a big sounding pipe with big bright tenors and a balanced bass. Overall a slightly tenor dominant sound. This type has a very big harmonic presence coming from the tenors.
Glen type – generally a more mellow sounding pipe; milder bass, bright ringing tenors – the two sounds tend to blend very well with the end result being a tenor dominant sound.
MacDougall type – generally a mellower sounding pipe; warm bass and very well integrated tenors – this type of sound is completely seamless, you can not hear the bass from the tenors but rather they blend completely together to form one solid tone. The harmonic character of this type of pipe tends to give the impression that the sound is coming from everywhere at once, it’s a much less focused sound than say the Glen or Henderson types; this results in some antitypical harmonics which are quite pleasing.
Shawn Husk provided me with a recording of his Kron Heritage pipes. Audacity tells me a pitch of low A ~ 479 Hz.
Kron Heritage played by Shawn Husk
His description is below:
2005 Kron Heritage (these have the newest bores; the original Heritage stands had problems with a rough sometimes growly bass, this was corrected in 2004/2005; my set has these changes)
Begg sheepskin bag, full set of cane drone reeds, McC2 with Higgins reed, overall pitch should be around 478. Recorded with a Zoom H2 in a medium sized bedroom.
This is what I would characterize as a classic big bold Henderson sound.
All the best,
All below are snippets of the album “Stiff Wind” produced by Trouble in the Glen back in the mid-2000’s.
Kron Standard, low A ~ 478 Hz -> This Kron standard is equivalent to an Atherton Glen. Rocket drone reeds were probably used.
Soutar, low A ~ 473 Hz -> No idea on the drone reeds.
Henderson, low A ~ 472 Hz -> Probably Shepherd SM-90 drone reeds.