1) Explain to students that most sounds in the world are complex, containing different tones and overtones which can span a range of frequencies. Ask students if they can think of a way in which they may have encountered sound broken down into its different constituent frequencies. (Accept all answers, but explain that the “bass” and “treble” adjusters on computers and audio equipment basically do just this by emphasizing higher and lower frequencies.) Explain that graphic equalizers on more sophisticated stereo systems go a step further by breaking down any given piece of music into varying numbers of frequency “bands.”

2) Load the “Frequency Explorer” widget from the MUSIC INSTINCT Web site. Play each sound in turn with the widget on the default (“reset”) settings, and then adjust the settings to emphasize higher, treble frequencies (on the right) and lower, bass frequencies (on the left). Ask students to describe how the quality of each sound is affected by adjusting the settings in different ways. For instance, does a cheering crowd sound nearer or further away without treble? (Further.) What might be deduced from this? (Higher frequencies don’t travel as far.) Can the sounds of an indoor shower be made to sound like rain outside? Can it be made to sound like an egg frying? (Accept all answers.)