The recorded sounds could be physically and electronically manipulated to alter them using the following techniques:
Sampling
A sound captured on tape can be isolated by physically cutting out the section of the tape on which it is recorded.
Looping
A section of tape containing a sound sample could then be made into a loop and both ends spliced together. This loop is played continuously to create a rhythmic pattern which is dubbed onto a second tape. This technique eventually found it’s way into the repertoire of the more adventurous rock and pop groups, for example, the track “Money” by Pink Floyd is based on a loop of seven different sound samples—paper being ripped, an old cash till, coins dropped into a bowl, etc—to create a 7/4 time signature.
Radiophonic engineer, Ray White describes in more depth, “This was an incredibly flexible arrangement, since any of the machines could be in recording mode. The tape could be drawn out as a loop between any pair of machines, or a tape loop could be created that returned from the third machine back to the first. Such a loop was conveniently held at tension by a special spring-loaded ‘loop stand’. This was a modified microphone stand with a sprung arm, the end of which contained a tape guide.”
Reversing
The original tape is played backwards. This completely alter the character of a note which, for example, may have a sharp attack and a gradual decay but now builds up slowly and ends with a ‘plop’.
Transposition
The original (or reversed) tape is played back at a different speed. For example, a sound can be recorded at 7½ips and played back at 15ips to shift the pitch up by an octave and halve the duration of the sound. Or playing back at 30ips to shift the tone up two octaves and quarter the duration. Sounds can also be shifted down in frequency by recording at high speed and playing them back slowly.
Filtering
Removal of frequency content by use of low-pass, high-pass or octave filters to drastically alter a sound or even make it unrecognisable. For instance, Derbyshire severely high-pass filtered white noise to give the “shimmering heat haze” backdrop to the Tuareg tribesmen weaving slowly across the Sahara Desert in Blue Veils and Golden Sands.
Vibrato
The tape can be played at varying speed to alter the pitch cyclically to create a wow and flutter effect. Wow is a low-speed variation (below 4Hz), and flutter is a higher speed variation (above 4Hz), which is often perceived as intermodulation distortion.
Reverberation
Reverberation or echo effects can be added to a recorded sound by playing it through an EMT 140 tube plate reverb, Binson ‘Baby’ Echorec magnetic drum echo-delay machine or the Maida Vale echo room (a small, cold and damp room located in the basement of the building with bare painted walls. The echo room had a loudspeaker at one end and a microphone at the other).
A method known as ‘feedback’ was sometimes employed. This consists of taking a feed from the replay amplifier back via a controllable attenuator to the input of the record amplifier. The delay is that of the physical separation between the two heads but can be further increased, and extra echo added, by allowing the tape to pass from the first machine and a cross the replay heads of any number of other machines before being taken up and spooled onto the final machine. Any or all of the outputs of the replay heads in the chain can be fed back in varying amounts to the first record head. A variety of flutter echoes may be obtained using this arrangement. The flutter frequency clearly depends upon the tape transit time from the record to playback heads and the rate of the decrement depends on the overall loop gain. Should this exceed unity, the system will build up to a distorted maximum limited by amplifier and/or tape saturation.
