Use a cardioid microphone and direct it toward the lowest key. To minimize key noise, place the microphone a little to one side of the instrument. The low mids and mids (between 800 Hz and 3 kHz) emanate from the keys only. As the pitch rises (upper mids and highs), more of the sound is generated from the bell. Frequencies generated by overblowing (above 5 kHz) are projected exclusively by the bell and will head straight for the ground. Therefore, a reflecting floor will provide a more brilliant sound.
