Phil Spector is famous for the ‘Wall of Sound’, He created this sound by having a number of instruments or vocalists perform the same parts in unison, then he would record the sound using an echo chamber. Some tracks were doubled or tripled to make songs sound fuller. He recorded in Mono during the wall of sound era. An echo chamber is a hollow enclosure used to produce echoing or reverberant sounds.
Here is an account of how a echo chamber is used:
‘Producing echo and reverberation in this form of echo chamber is remarkably simple. A signal from the studio mixing desk — such as a voice or instrument — is fed to a large high-fidelity loudspeaker located at one end of the echo chamber. One or more microphones are placed along the length of the room and these pick up both the sound from the speaker and the echoes of it that bounce off the walls of the chamber. The farther away from the speaker, the more echo and reverberation the microphone/s will pick up and the louder the echo becomes in relation to the source. The signal from microphone line is then fed back to the mixing desk, where the echo-enhanced sound can be blended with the original “dry” input.’ (wikipedia, 2010)
I have found a number of videos explaining and showing the wall of sound.
Wall of sound documentary:
Unfortunately Phil Spector didn’t really evolve his techniques much and received negative comments from the Ramones.