It’s all about making everything fit into the spectrum of frequencies. If you subtract something from one instrument, it might be wise to add it to another. For instance, if I take the upper mids out of a guitar so it won’t thrash your ears as much, I’ll add the same back to the cello. The cello produces a lot of low end anyway, so that just makes it come out more.
FixIt: Adam Fisher, Polyphonic Spree FOH Engineer
Read front of house engineer Adam Fisher's Live Sound Tip on Making Sure that All Instruments Fit Into Spectrum of Frequencies during Polyphonic Spree tour