Do all bagpipes sound the same?

The short answer is no. From here on, it gets more challenging to explain...

The tonal quality of the bagpipe itself depends upon the development and transmission of harmonics of the basic frequency of the drones and the blend of those harmonics with each other and with the tonal characteristics of the chanter. Reed selection and set-up have a strong impact on the input to this system. The drones serve to shape that sound. If the sound is not present in the reed, the drone cannot create it.

For the drones, the dimensions of the stocks (both length and diameter), the inner dimensions of the bores, the shape of the bell inside the top of the drone and dimension of the bushing at the top all affect the tone.

The finish of the bore also plays an important role in the tone of the instrument in that any "roughness" in the bore tends to reduce the strength of the upper harmonics. (See oiling or polishing the drones, below.) The tools, the wood itself and the workmanship can all affect this aspect.

The chanter tone is affected by the internal dimensions, particularly in the throat region and in the bell.

At any given time within a manufacturer's line, the internal dimensions of the instrument are (generally) nominally the same and any sound difference between a basic set and a more ornate set is generally not intended. There will be modest tonal differences between individual sets of pipes from the same manufacturer because of slight differences in the wood and minor variations in the manufacturing process due to the use of multiple lathes, multiple machinists and tools - each with the opportunity for differences.

Between the different manufacturers, there are significant differences in the tone. The manufacturers each have a goal in mind for their tone and they adjust the dimensions to achieve that goal.

There will also be some difference between older and newer sets from the same manufacturer as they evolve their goals and designs. There are many cases where a new shop manager will be hired and will mandate a change in dimensions and design to move toward a different sound.

The hardness, density and grain structure of the wood are very important to generating a smooth finish to reflect the sound wave. African blackwood is generally considered most suitable for many musical instruments. However, blackwood density also varies from tree to tree depending upon where and how it was grown. In the old growth forests, competition for sunlight lead to slow growth and dense wood with very fine grain. These forests are largely gone and modern production farming of these woods is done to maximize the amount of wood, not its density. This may be why the "old" instruments have a certain "something special". Here's an outstanding link describing different species of "blackwood" including mpingo and grenadilla. Ebony is also a very dense wood, but can be prone to cracks especially in warmer climates. There are pipes made of oak, maple, keranda, mopane and cocabolo which may be very nice depending upon the manufacturer and design. (One of the most stable set of pipes I've ever played was made of keranda wood!) Older pipes made of cocus wood were common in the late 18th and throughout the 19th centuries.

An additional minor factor in tonal difference, recognized by at least one highly regarded manufacturer, is that there will be a "maturing" of the tone in a wooden instrument following the manufacturing process. As a first step, the rectangular wooden "blanks" for drones are commonly drilled out and allowed to age for up to several years to remove excess moisture from the wood. The wood will change dimension and density during this period. Following the final boring and turning of the piece to convert it to a drone, there will be some very small additional changes which can affect the final dimensions and density, thus affecting the tone.

There are also a few manufacturers of plastic (polypenco) bagpipes. I strongly feel that these instruments (e.g. Dunbar in Ontario) have a lot to offer. The tonal quality of these sets can rival much more expensive instruments. I have a set that I play in parades and in foul weather.

At the lower extreme, there many bagpipes manufactured in Middle and/or Far East which have a very poor reputation for sound. The problem with these instruments is generally a combination of soft wood, poor workmanship and marginal design. (Note: Each year I'm asked by one or two people who've bought these instruments to help make them more playable. I've found that these instruments often lack the ability to resonate well. Such an instrument can never be steady. Even in "tip-top" shape (for me!), I can only play these instruments for a few minutes before I'm exhausted by the amount of air they take and the frustration of trying to play with a steady tone. I've concluded that it's very much what's on the inside that makes for a set of pipes. Also, the chanters on these instruments are universally horrid - flat, squawking and lacking in richness. I've never seen one played in public - and hope that I never do!) These pipes are generally made of Sheesham wood (a soft, reddish wood from the middle east) though some are made of rosewood, black rosewood, cocus wood and black wood. Oddly "black wood' is usually not "black" until it is stained and/or painted....