The A-B technique places two mics parallel to one another, spaced apart anywhere from a few inches to several feet. Mics may be omni or cardioid, though omnis are more common to the point that the technique is often called "spaced omnis."
A-B come in many varieties, the one shown above is the most commonly used in the DOM. Two omni-directional mics (designated by a "circle") or two cardioid mics (designated by a "fat heart") placed 1-3 feet apart and PARALLEL to one another on one stereo mic bar. Because omni mics pick up sound from 360 degrees, they will capture more room ambience than a cardoid (directional) in the same position. This technique finds use up close on the piano (Avenson STO-2s, M-Audio Sputniks, Neumann KM184s), on jazz band horn section (Neumann KM184s), a few feet back on solo piano (Avenson STO-2s, M-Audio Sputniks), and various recitals/concerts as a main pair. Probably not the best technique for percussion ensemble in PAH, but not bad in Lovett. Omnis are sometimes spaced very far apart several feet to either side of an ORTF or NOS pair on large instrumental ensembles (then they are referred to as "outriggers").
