Tape delay units were large, yet (trans)portable tape recorders that incorporated a recording head and a playback head. While the guitar player is playing the original signal is recorded by the recording head and then it passes through the playback head milliseconds later creating the delay effect. The length of delay depended on the distance the tape had to traverse between the playback head the recording head.
This technique was utilised in the mid 1950s to create the “slapback” echo effect that defined the rockabilly sound and many early rock & roll recordings. To create slapback the delay is set for a repeat rate of about 150 to 200ms with just one repeat at almost the same amplitude as the original signal. A good example of this can be heard on Scotty Moore’s guitar-work on “That’s All Right” by Elvis Presley. The sound engineer at the time, Sam Phillips was to use this effect on many recordings and it became a trademark sound of Sun records.
At this time there were several innovators developing portable delay units based on magnetic tape technology, notably Charlie Watkins (inventor of the Copicat) and Ray Butts (Maestro ‘Echoplex’). Now delay could be used in live sound applications. As these units developed over time they started adding more playback heads and tape speed controls giving delay more flexibility than it had ever seen before. With the addition of more tape playback heads delay could now feature more repetitions (multi-tap) of the same signal instead of just one. The addition of speed control or movable playback heads allowed for the first time the flexibility to change the delay speed on-the-fly. Many of these units are still used today in recording studios and sometimes in a live situation although this is rare.
This section would not be complete without mentioning the Binson Echorec, which was considered the top of the range echo unit for its time. Binson, Milan, Italy developed a storage medium based on a steel/alloy disc or drum, which carried a durable flat metal band around its circumference. This offered a significant improvement in terms of stability over tape delay. The Echorec was utilised by many artists, such as David Gilmour to create spacious and ambient sounds which literally defined the Pink Floyd sound during the 1970s.