610 Recording Studio Design 24.3 Stereo or mono Without doubt, a stereo foldback presentation is easier for musicians to work with compared to an `above the head' mono jumble. In general, because of the spacial separation, individual instruments can be readily detected in a stereo mix even if their level in the mix is on the low side, or if they are in a frequency range which is shared by other instruments which are playing at the same time. Nevertheless, mono foldback is still common, especially when multiple mixes are needed, as there may not be enough auxiliary outputs or foldback channels to send stereo feeds to everybody. Mono mixes usually require much more delicate balancing if the musicians are to hear the detail that they need, and it is often wise not to send unnecessary instruments to the mix. Simplicity can be the key to clarity in mono mixes. Some recording engineers, when overdubbing, send a stereo feed to the foldback which is derived from the monitor feed in the studio, plus a little extra boost on what is being recorded. This system can work well, but it must be done in such a way that any muting or soloing on the main monitors does not affect the foldback, or it can be very disturbing and frustrating for the musicians. It may also, at times, be an inappropriate balance, because perception via headphones can be very different to perception via loud- speakers. Once again, though, if the engineer has a headphone feed from the same power amplifier output that feeds the musician's headphones, then the appropriateness of the balance can readily be checked.