Once or twice, I’ve had students insist to me that a Cb is the same as a B. Each time, I have to remind them that, actually they’re not the same note at all and as singers it’s very important to remember that.
Now, many of you may go “huh? I thought a Cb and a B were the same note? They’re the same key on a piano!”. They are indeed the same key, but they’re not actually the same note. As a t-shirt I bought in Thailand says “Same Same, But Different”.
About 300 years ago, Western music adopted Equal Temperament. In essence, this is where all instruments (pianos in particular) are tuned so that all intervals are exactly the same*, even though in the natural world, they’re not. So your beloved piano is, by the wonders of modernity and our desperate need to enforce order in a chaotic world, tuned slightly flat at one end and sharp at the other. So, in the world of equal temperament, yes, a Cb looks and sounds and sings like a B. But it’s not a B.
Outside our crazy, regimented Western music, a Cb is fractionally higher than a B. Which brings us back to bagpipes. Bagpipes are not tuned to equal temperament! They’re tuned to Just Intonation (or, as I like to think of it, left in their wild slightly-unharmonious natural state). This is why their intervals sound slightly strange to us, as though they’re not quite in tune. In reality, the bagpipes are actually -in- tune, and the rest of our music isn’t. Kinda.
Acappella singing also tends to drift towards just intonation. I suspect this is why it’s blindingly obvious when TV shows and films like Glee and Pitch Perfect use voice samples plugged through a keyboard to fill out the acappella singing. It just doesn’t sound right, and I wonder if it’s because actually, true acappella singing is justly intonated, not equally tempered.
So there you have it, a short explanation of why bagpipes sound weird, and also why the voice is the most flexible instrument out there – it can be equally tempered and justly intonated without any trouble.
If you want more, the Wikipedia pages are pretty good, and I believe Ross Duffin’s How Equal Temperament Ruined Harmony and Why You Should Care comes pretty well recommended.
*The intervals are not all the same length because the frequency ratios differ slightly for each pair of notes. Equal Temperament is an average ratio, based on the ratios of the note A, which has nice neat frequencies of 110hz, 220hz, 330hz, 440hz etc. For a more detailed explanation, see the Wikipedia page, or speak to a music teacher!