Setup
A Decca Tree setup includes 3 omnidirectional microphones in a "T" pattern. The stem of the T faces the orchestra, and the left and right mics are placed about 6 feet apart. The third is placed 3 feet out and centered in front. To mix, the side mics are panned hard left and right, and the output of the centre mic is then sent to both left and right channels. The level of the centre mic is set sufficient to fill in the centre "hole" left by the widely spaced outer mics, but is not so high as to cause an overall mono sound to the recording.
The Decca Tree was originally used in orchestral situations, fitted on a tall boom and suspended high up in the air, roughly above the conductor. Three separate stands were sometimes used to set individual heights.
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