The Great Highland Bagpipe has a range of only one octave + one note. Why is the range so limited, and would there be a way to increase it?
The number of notes depends on the number of fingers available to close holes with, remembering that you don't want to drop the pipe either. It also depends on the size of the hand.
In theory lengthening the chanter and adding holes would give a longer range. This might mean adding a key system so that more holes could be managed with a limited number of fingers. There is already a large difference in tone between the top and bottom of the range; this would be larger, but people could get used to that.
The piper obviously does not have the option of using lip pressure to change the note as an oboist does, and cannot change the air pressure too much either because of the effect on the drone pipes.
Why is the range so limited?
The part of the instrument responsible for generating the main notes is the chanter. That is the part the piper plays. The three drones, two tenor drones tuned an octave below the chanter keynote (low A) and a base drone two octaves below the keynote, do not change pitch.
The chanter produces notes according to the spacing of the holes and the volume of the pipe. These are low G, low A (usually in the range 470-480 Hz), B, C#, D, E, F#, high G, high A, so basically a D major instrument. The physical characteristics of the chanter (the volume of air inside it which can be set vibrating and the way that volume can change via the holes) determines the range and pitches available.
would there be a way to increase it?
Increase the length of the chanter and introduce more holes suitably spaced.
In other types of bagpipes (Flemish, Galician, English) the compass is wider than the 9 notes of the GBH. The reed can be forced to 'overblow' by a momentary increase in bag pressure, giving a range of an octave and a fourth or even two octaves in the case of the gaita.
I'm not an instrument maker so am happy to be contradicted, but I believe this ability is down to the internal profile of the bore of the chanter and the chanter reed construction, rather than just the length of the chanter.
There are some possibilities to increase the number of tones for a woodwind instrument:
- Increase the number of holes: things become tricky, since holes left open (e. g. due to lack of additional fingers) limit the effect of other closed holes.
- This is why keywork helps: the connected springs close holes automatically, so the fingers have a choice, which hole to open - alas, no bagpipe I have seen provides any keywork. (The other important purpose of keys is, that holes with bigger distances can be managed.)
- Overblowing; whether this works depends on a number of parameters.
- A acquaintance of me, who plays Scottish bagpipe, assumed, that the form of the bore (conical or cylindrical) has an influence.
- It is also clear, that the resonator (here the reed of the chanter) has to support the double frequency of resonating (in case of an open tube) or even the triple frequency in case of a tube closed at one end (as clarinet). Scottish bagpipes are not observed to be played using overblowing; not even the practice chanter, which is blown directly - as opposed to mediated by a bag - allowing the same control as other reed instruments. Assumption: the reed may be simply to inflexible to resonate so fast for other conditions as intended volume.
- To establish the intended overblow frequency, some instruments sport as special overblow key
- The increased air pressure must be provided; since bagpipes have drones besides the chanter, which also require air, the arm pressure on the bag may only supply the increased pressure for a short moment, before ther air is exhausted.