we may need to add a denormal k to MidEQ ( z = SynthDef(\MidEQ, { arg outbus=0, ffreq=1200.0, rq=1.0, db=0.0, amp=0.1; Out.ar(outbus, MidEQ.ar(AudioIn.ar([1,2]), ffreq, rq, db, amp)); }).play ) z.set(\db, 3.00) // freq boost - as expected. z.set(\db, 0.00) // last freq boost still in effect z.set(\db, -3.00) // now -3dBs z.set(\db, 0.00) // still -3dBs greetings, x