**PURPOSE: **To demonstrate the relation between "consonance" (musical intervals) and frequency ratios.

**DESCRIPTION: **Two identical oscillator/loudspeaker setups are sounded and simultaneously input into the two axes of an oscilloscope to produce a Lissajous figure. Two pitches which are related by simple rational whole numbers such as 3:2 or 5:4
are musical intervals and produce stationary figures. Beats between two close frequencies are also visibly evident by this technique. Try two close frequencies and two related by a small whole number interval for contrast. Let your students judge their
consonance.

**SUGGESTIONS: **

**REFERENCES: ** (PIRA
unavailable.)

**EQUIPMENT: **Two oscillators with loudspeakers and oscilloscope with scope/TV cart.

**SETUP TIME: **5 min.