5.7.4 Approach to recording The purpose of the recording and the rules of the particular discipline to which it belongs will govern many aspects of recording approaches, microphone techniques and the like. There are, however, a number of common concerns in making such a recording. Field recordings usually record or document a given situation and under these circumstances the original dynamics of the documented action should be respected in the recording as well. Audio input levelling should orientate on the wanted signal, and not the general background noise, and continuous adjustment of the level during a recording should be done judiciously, if at all. Use of automatic gain control functions is not recommended as such features falsify original dynamics by raising low level parts (and therefore noise) and reducing the wanted signal dynamics. Likewise any limiters used in a recording should be applied cautiously. A well adjusted limiter will rescue the recording if an unexpected high level signal is captured but have absolutely no impact on the majority of the recording because it is not triggered by the level of the recording. On the other hand, a poorly adjusted limiter may simulate a perfect level on the meters of the recording device while the microphone itself may already be overloaded due to the input signal.Whenever possible, manual levelling is to be preferred and any limiter, adjusted so as it has no impact on the normal signal, only switched in after an optimum level has been achieved.  When making a recording where the signal is embedded in a noisy environment advantages are to be found in using standard stereo microphone arrays. There are many approaches but those that are briefly discussed here include near-coincident technique of which ORTF (Office de Radiodiffusion Télévision Francaise) is an example, XY crossed pair,AB parallel pair and MS (Mid-Side) techniques. ORTF seems to be most useful where analysis and evaluation properties of the documentary recording are an important requirement. In this technique the microphone capsules are separated by 17cm at an angle of 110º. An ORTF recording, when analysed via headphones, enhance the ear and brain’s ability to trace a wanted signal within a noisy surrounding; the so called “cocktail party effect”. The head-related binaural microphone array imparts the extra information and so helps identifying wanted signals in noisy sound fields. Also, as the specification for ORTF is defined, the microphone set-up can be much more easily replicated in a standard way.  Standard XY crossed pairs are arranged so that the microphone capsules are as close together as possible, but pointing at least 90º away from each other. The intensity of the signal information is recorded, but ideally no phase difference is noted. This technique produces a recording that reproduces well on speakers, but does not have as much separation information as other techniques. AB parallel pair uses two omni-directional microphones in parallel separated by around 50cm. This technique has been favoured in very good acoustic environments but will rarely produce acceptable results in very noisy environments. It may have phase cancellation problems when summed to mono.  MS (Mid-Side) technique places a bidirectional microphone (figure 8) at right angles to the sound source, and a cardioid pick up pattern microphone (or sometime an omni directional microphone) pointing at the sound source. The two recorded signal may then be manipulated to produce mono compatible stereo recording (M+S, M-S). If recorded as MS information, the signal may also be manipulated after the event, and so gain some control over the apparent spread of microphones.  Some situations, where the exact nature of the event is unknown prior to the recording being made, can take advantage of movable directional microphones, multi-microphone techniques and multi¡track recording. Interviews may use two microphones pointed at the participating individuals, which presents very acceptable recordings. Clip microphones are, in many cases, less useful, as they pick up unwanted noise from body movements, breathing, clothing and jewellery, and record little or no information about the environment in which the recording was made, which is often an integral and necessary part of the field recording.  Microphone techniques contribute to the quality of the recorded content and this very brief consideration of them is only a guide to the possibilities. It is recommended that all those intending to make recordings in the field should become familiar with the possibilities afforded by good microphone techniques before making important recordings.