I’m curious whether bass drone slide sections can be changed without affecting the sound or stability of the bass.
For example, if I have a straight bass drone, and if I don’t like straight bass drones (too long, doesn’t suit my posture, etc.), could I replace just the slide section with a U-shaped slide, without affecting sound or stability?
Probably.
Some length considerations might be needed… sometimes the change of diameter into the ‘return’ feed pipe can mean that its length addition may make little overall difference to the effective pitch of the pipe.
Tonal changes can also be made; the effects of a Puck that is hollow, or not, the length and diameter of return tube, can all affect the outcome.
Perhaps a change of Reed may be required.
A friend of mine did the contrary (replaced the U-shaped slide with a straight one) on his Kennedy set and it changed nothing.
All other things being equal, a bend in itself will not change the sound. For instance if you were to unfurl a french horn so it was straight, it would still sound like a french horn.
RORY
A curved bore is almost the same as the equivalent straight bore, but not quite. In theory a curved section acts both wider and longer than a straight section of the same diameter (according to Benade). As Geoff suggests, it should work “more or less”.
Note that most straight bass slides are quite short compared to a bass with a ‘J’ bend, so you may find this awkward in practice (puck collides with regulator caps, etc.). A straight vs bent bass configuration usually has different lengths on the other sections as well.
All that said, I did replace the straight bass on my personal concert pitch set with an equal-length ‘J’ slide, to make it more compact. It sounds nearly identical, fits into a viola case wihout disassembly, and the bass is easier to shut off with a finger.
-B
I’m not sure if you’re right about that Rory. I’ve heard people say that bent woodwind instruments like the basset horn have a more hollow sound. And the french horn always sounds a bit muffled to me. And if you remember, I posted pictures of a weird chanter with a really bendy bore a few months ago. It works o.k. but I think it lacks some harmonics:- it’s hard to tell for sure until I hear a real piper playing it. I going to make another one with some proper tone wood instead of the scrap wood I used last time and hopefully I can also improve the build quality. Maybe that will improve the sound.
As Bill Haneman observes, a bent drone slide needs more length for the same pitch. Better minds than mine have tried to analyse the problem and they conclude that the (low frequency) standing wave in the bend likes to live on the inner curve, effectively taking a shorter path. That’s why more length is needed. Thank our lucky stars that we are only dealing with the single note of a drone. The whole thing gets a bit crazy over a range of octaves and the upper partials; the displacement in impedance peaks depends on frequency, some moving up, some down. A straightened French horn would sound the same (almost) but its tuning would be out.
Well I don’t want to argue with the experts PCL but my experience is the entire opposite! The tone of my bendy chanter is a little bit lacking maybe but the intonation is bang-on. I can even get a high C nat (off the knee) with the same cross-fingering as the lower octave, so I don’t know what’s going on.
I’ve three guesses:- I’ve used a “squinter” type construction so maybe the extra impedence caused by the square cross-section is cancelling out the “bend” effect. Strange that it cancels out exactly though. The other guess is that the bends to the left are cancelled out by the bends to the right so those low frequencies would have to “cross over” in order to hug the inside of the bend (but the overall route might still be shortened). Third guess: the bore isn’t square all the way down. Geometry dictates that the bore is trapezoidal in cross-section a lot of the time which might have the effect of making the bends longer. ( i.e try imagining the centre of gravity of a trapezoid - in some cases it’s going to be off-centre).
There are two ways to look at it ,one as a mathematician and the other as a musician .As far as a musician is concerned bending tubing does not change the pitch or tone in any way.You can see this for yourself by electrical taping a drone reed into a piece of garden hose, with the hose straight blow the reed to get a steady note, continue blowing as you curl the hose into tight coils ,the tone nor pitch change.
A mathematician would say the pitch is raised as you coil the hose because as it is curved the inside curve is compressed relative to the outside curve ,this reduces the internal volume of the hose and it is this that on paper raises the pitch,not that the waves decide to take a short cut around the curve. The percentage by which the volume is changed by bending is very small and of no consequence.
RORY
I thought that mathematically, if you bent a straight pipe into a circular curve the loss in volume from the inner part being compressed is equal to the gain in volume from the outside part being stretched. This is why the formula for the volume of a ring torus is the same as a straight tube that has a length equal to the torus’ circumference. I would totally believe that a bent tube has a different impedance for air flow than a straight one though.
There are more variables than cross sectional area vs length operating here. There is also radius of the bend, cut-off frequency, impedance of the bend, the location of pressure maxima and minima, and, possibly, the mode of the reed. We cannot over-simplify. That said, consider a wavefront sweeping round a bend. If the bend has too tight a radius, the speed of the wave on the outside of the curve has to increase for the wavefront to be maintained. Now what happens if that means the speed of sound is exceeded? The wavefront has to “bunch up” in the slow lane, on the inside curve, and take a shorter path. What practical difference this makes is an open question. On the bass drone, the slightly larger bore of the metal tube U-bend may be a dominant factor in raising the pitch.
Geoff Wooff put it succinctly above.
Getting back to the original question posed by PJ, a U-bend drone slide should work. If not, make a new drone reed. Things could be worse.
Anyone like to have a stab at this one. Hypothetically speaking is air flow essential for a woodwind instrument to play or is the air flow just a by-product of the excitation method ? Say for instance you had a magic reed that would vibrate without blowing it ,or were able to introduce a sound similar to a reed crow into the chanter without airflow ,would the chanter play?
RORY
A loudspeaker at the end of the pipe would be just such a magic reed. You can observe resonance effects in the pipe as you change the pitch coming out of the loudspeaker, but the resonance doesn’t affect the pitch from the loudspeaker, so it doesn’t play like a chanter.
Air reeds (flutes and whistles), lip reeds (trumpets and other brass), and cane reeds (bagpipes, oboes, clarinets, drones,…), all require air flow to operate. For all of these, the resonance effects in the pipe affect the pitch coming from the reed because the waveform in the pipe affects the air flow in the reed. Changing the resonance changes the pitch, so the chanter plays.
In principle, you could connect a feedback loop from the pipe to the signal generator driving your loudspeaker, so that resonance in the pipe affected the pitch, without air flow. Possible, but not high on my list of things to try.
Sound is energy, so you need some way of making the reed vibrate to make the sound. One could imagine a little mechanical device that does this, or some magical demons that slap the tongue of the reed down (drone reed; they’d have to be quite acrobatic to work a chanter reed). The pressure pulse born by the slap of the tongue is reflected (in a complex way) from the open end of the drone and pops the reed tongue back open. The demons, or device, slap it down again and the process repeats. It is easier to use moving air (Bernoulli’s principle). The flow of air in the bore has no effect on the generation of the standing wave. Except in a hurricane.
Re bendy pipes. There are some interesting and possibly conflicting opinions in this thread. My experience seems closest to Rory’s: i.e you put a bend in a pipe and not much changes (except that he is talking about parallel tubes whereas I’m talking about conical). One extra bit of information would settle it for me:- whilst my bendy chanter is in tune with itself, I have no idea if the overall pitch has been raised or lowered compared to the “straight” original. The chanter is based on the Kenna C which is described in the Sean Reid Society Journal. The Journal has a recording of the drones but not of the chanter. The drones appear to be sounding about 10 cents sharp of concert C which is about the same as my chanter when it’s warmed-up (10 to 15 cents sharp). Does anyone know where I could find a recording of the chanter or maybe know who currently has possession of it?
There are to many interactive variables involved . To pin down a 10cent sharpness to just one cause is probably unsafe.
RORY
I agree. I was just wondering if the original played at minus 40 or 50 cents or something. But since I last posted I dug around the Chiff archives and it seems other people’s copies have ended up around concert C so I guess I’m not far off. Onwards and upwards.