Marshall Electronics MXL-FR-400 Boundary Microphone, 50Hz - 16kHz

Although it's commonly used in front of a stage to pickup concerts or theater events, the FR-400 boundary mic has a wide cardioid pattern and can be used in other applications like under the lid of a piano. The switch located on the bottom of the mic can be used to boost or cut low frequencies by 6 dB in order to balance the frequency response.