Spectralism is a type of composition that is organized by taking as its basis aspects of the harmonic series, or the overtones resulting from a sounding pitch. From the ’70s onward, composers, many of them residing in France or Romania, have looked at spectrograms of sounds to plot out the harmonies that they will deploy over time in a piece. This may sound rarified, but it is also one of the oldest traditions in music. Early humans listened for resonances, particularly in caves, some even using conch shells (brought in from many miles away) to create loud enough sounds to hear lots of reverberating overtones. Throat singers manipulate their voices to sound more than a single pitch at a time. If you have ever heard a bunch of higher sounds…