Too loud?

As a one-time organist, I should have known this, but the expression "to pull out all the stops" comes directly from the business of playing an organ.  Those knobs which you see running down each side of an organ keyboard are called stops, and you pull one of them out to couple up a particular series of pipes, and equally push it back in to decouple them.  Each series of pipes adds to the overall volume, so pulling them all out gives you maximum volume, and there you are.