During producer/engineer Frank Filipetti’s seminar on using the Universal Audio UAD-2 card during mixdown, which he presented at Sweetwater’s recent GearFest ’09, he had several tracks set up with more than one compressor on each track. For example, the lead vocal had two compressors in series. (One of the beautiful things about plug-ins is that you can have multiple instances of various things open and operating at once — try that with a hardware compressor!) This way, each compressor can be set up to more gently process the signal, which reduces artifacts in the final signal.