The need for audio engineers to make tracks sound as if they are coming from various types of acoustical environments is as old as audio production itself, and has only intensified with the use of audio in film. Of course, when shooting for realism, the initial (and still the best) solution was to actually record the sounds in those environments – concert halls, theaters, living rooms, vehicles, etc. Then studio engineers like Bill Putnam Sr. and the like thought, “Hey, we have this facility with all kinds of rooms – why don't we play back an audio signal miked in a dry room (one with little reverberation) into a wetter (more reverberant) room with a loudspeaker and mic the results?” And thus, the art of applying additional reverberation to tracks was born. The process has undergone a great deal of mutation since then, with the creation of reverb devices utilizing anything from metal plates, springs, a series electronic delay lines, all the way to modern digital equipment with powerful IC's.