"ORTF" is an acronym for a French broadcasting organization, and designates a method they devised for stereo recording using a pair of matched microphones. This stereo microphone technique is often used when you’re recording a large source (like and orchestra) that will have level and some arrival time differences between left and right. The TD-93 provides you with the proper ratio between microphone distance and angle ensuring proper placement for true ORTF recordings. You will need to supply your own mounts to use this stereo bar.