An echo room chamber is a space where program material is played and the reverberations are captured on a microphone. You know the classic sounds of a good church or music hall. Studios needed to capture these effects without always going to a church or hall to record. So, they built their own echo chambers. The famous EMI/Abbey studio had 3 echo chambers. They also used electronic filters to carefully refine the sound in order to make it easier to record, which made the end results sound impeccable.