How can two singers sing the same song in the same key still have distinguishable voices?

Question

This is actually question my daughter posed and I’m pretty stumped. She asked how, if two people with (let’s say) perfect pitch sing a song, how is it possible that we can still tell who is singing when the notes would be identical?

Note: I know absolutely nothing about music, but figured this was the best place to ask for her.

Edit: Wow, many of these answers are incredible! I had no idea this would receive such in depth and thoughtful feedback. I have learned a huge amount. I was not exaggerating above when I said I know nothing about music (I don’t even know what pitch is – just quoted my daughter on that) and I’m grateful to those of you who took the time to help me learn.

In: Biology

Answer 1

Something nobody else has really touched on in depth: Waveforms.

So in really basic electronic music, you’ve got sine waves, sawtooth waves, and square waves. Every note is literally just a pulse of air at a given frequency. It’s why car engines, which are literally just exploding aerosolized gasoline, make audible notes.

There are videos you can search (I’d link one but I can’t right now) that show the relationship between frequency and pitch.

**So what does that have to do with a sine wave?**

Well the waveform is what the sound wave actually looks like. A square wave is completely no noise, then immediately completely 100% energy, then back to complete silence. A sawtooth wave is like a square wave at first, but instead of staying at 100% energy it trails to zero over time. A sine wave is just a very rounded (sinusoidal) square wave so the energy changes are smoother.

And all of those waves have different timbres, or tones.

But if we layer a sawtooth wave with a sine wave, or we decide to cut a huge divot in the top of a sine wave, you’ll get different tones still. Playing with these waveforms is precisely how electric keyboards attempt to synthesize other instruments.

Okay so now we can step away from the electronic sounds, and go back to the natural world. Horns, car exhausts, and the human throat all have characteristics that make their own wave form. There are so many things that can affect which frequencies are highlighted and which frequencies are subdued. You can choose to manipulate those with tongue placement and mouth shape, or bell shape and pipe length or construction material.