Posted on 
Feb 05, 2003 11:19 am Izotope recomends starting attack around 10ms and release around 100ms and adjusting from there. On atack if you lower the value it will "soften" the sound of the instrument. You will get less transients or sharp edges of the sound you are compressing. A fast release can create an unatural emphisized sound depending on the sustain of the instrument. And yes, you are right, it's back to the ear for final decision.