I am in the on-stage engineer for my band and all our live instruments go through an fully automated submixer linked into Abelton Live where they have been optimally mixed for each song. This is then sent as a stereo signal to the FOH desk, and all the FOH engineer needs to worry about is mixing the vox with the stereo mix (technically identical to mixing a vocalist over a backing track, except in this case this the backing track is played live). Because the instrument track level settings are instantly recalled in Ableton Live for each song, we should in theory be able to set up anywhere, plug into the FOH system and play each song perfectly without really having to sound check other than getting a decent balance between the live vox and the instrumentation. However, we are getting conflicting comments about our live sound. The punters love it - no one has ever complained about the levels, although some FOH sound engineers have voiced concerns over the mix and complained that they needed to cut or boost certain instrument levels, but obviously couldn't because all they have control of is a stereo mix. What I am struggling to understand is, if the FOH desk and PA have been EQ's correctly to attenuate any undesirable frequency responses in the venue, then how can our overall sound be problematic when we have sub-mixed it perfectly? Surely the only potential issues would be vocal mic frequency placement and feedback which the FOH engineer has full control over?