mixed into two channels the mix generally involves first panning in amplitude the monaural signals individually so as to position each instrument or set of instruments in a particular spatial region in front of the listener in the space between the loudspeakers then ambience is introduced by applying artificial stereo reverberation to the pre mix in general the left and right impulse responses of the reverberation engine are mutually de correlated to increase the impression of spaciousness in this description we refer to two channel signals as left and right for the purpose of convenience it should be noted that the distinction is in some cases arbitrary and the two signals need not actually represent right and left stereo signals the second class or live recording is done when the number of instruments is large such as in a symphony orchestra or a jazz big band and or the performance is captured live generally only a small number of spatially distributed microphones are used to capture all the instruments for example one common practice is to use two microphones spaced a few centimeters apart and placed in front of the stage behind the conductor or at the audience level in this case the different instruments are naturally panned in phase time delay and amplitude due to the spacing between the transducers the ambience is naturally included in the recording as well but it is possible that additional microphones placed some distance away from the stage towards the back of the venue are used to capture the ambience as perceived by the audience.