The AM band is more important than the FM, but it does not matter if the radio picks up both. Older radios are usually better than newer ones—look for one built before 2000. The inspiration for the Cracklebox springs from the out-of-body experience of an adolescent Michel Waisvisz playing his father’s shortwave receiver by laying his hands on its 240-volt-powered circuit board. A tickled radio often swoops over a very wide frequency range, but if the built-in speaker is small, one might never hear the bass end. The coil will pick up lower frequencies than a small speaker will actually reproduce. Alternatively, drop an amplified contact mike onto the speaker: listen as it bounces around, adding a percussive edge to the radio’s squeals—like the bottle caps around the calabash of an mbira. The primary electronic function needed to transform the radio into an oscillator is amplification.