Studio Sound Techniques
Making tape loops.
Tape loops have always been a bit of a mystery to a great many people, historically, they go back a long way to the early pioneering days of Musique Concrete in the late 1940s and early 1950s. Pierre Schaeffer, Pierre Henry and Karlheinz Stockhausen were among the first composers to work with them.
A tape loop is simply produced by recording a sound onto a piece of magnetic recording tape, the desired section of sound located on the tape and cut out. Having removed the section of tape, you splice it together to produce a loop, which can then be placed onto the tape machine and played so that the resulting sound repeats over and over again as the tape passes the playback head.
The application of tape loops has mainly been confined to the area of avant garde music and saw little use in the world of commercial music until the late 1960s. Loops provide an interesting starting point for experimental music and are particularly useful when employed as a rhythmic backing.
Producing a tape loop is no more difficult than splicing a normal tape, the loops are usually made from ¼ inch wide tape and can be any track format. The April issue of HSR covered the techniques of splicing and editing tape, so we won't go over that ground again.
If you want to make a loop of the word 'Cat' you must first record it onto tape. Locate the beginning of the word and mark it with chinagraph pencil. Locate the end of the word and mark that as well. Cut the tape on the marks and remove it, place the tape in the splicing block and join it together making sure that you don't twist it. The loop is now ready to be played.
With the word joined together without any pauses at the beginning or end, you will hear the word 'Cat' repeated in close proximity. By inserting a piece of blank (unrecorded) tape or leader before or after the word, you can introduce pauses of precise timing. This effectively allows you to control the rhythmic tempo of the sound.
The sound quality will be better on loops recorded at high speed (15 ips) but this uses a lot of tape and makes the loop difficult to handle. Loops can be used in a variety of creative ways, for example, you can record a sound at 15 ips and play it back at 7½ ips, thus lowering the pitch of the recorded sound by an octave. Obviously the same is true for the other way around. Sounds may also be reversed which can be achieved by just turning the loop upside down, in fact, the first time you play the loop you've got a fifty percent chance of it being the wrong way around anyway!
The length of the loop can vary enormously. The shortest loop will be defined by your tape recorder and is dependent on the spacing of the tape heads (Figure 1). The longest loop can easily be around 20 feet long though they do get pretty difficult to handle.
Before you can start to play loops you will need to collect several props. For small loops you need a pencil and, if possible, the sucker off the end of a child's bow and arrow set. Medium length loops require a milk or wine bottle, and long loops need microphone stands.
Tape recorders vary from one manufacturer to another, possibly the best machine to play loops on is the Revox A77, because you can switch off the reel motors. By doing this you stop the spools rotating and therefore make it much easier to play loops. For tape recorders without this feature the alternative is to place a small empty spool on each hub, to help guide the tape. Any tape guide arms should be set to the normal position they would be in when playing a tape and fixed in place with sticky tape, if they are not in this position a cut-out switch normally comes into operation and will not allow the machine to enter the play mode.
To play a loop, first thread it past the tape heads and between the capstan and pinch wheel in the usual way. Hold the loop just taught with the aid of a pencil (Figure 2), set the tape machine to 'play' and you should hear the sound on the loop. The secret of playing loops is getting the tension right, this is something that you will develop a feeling for. Too loose, and the volume level will drop and cause modulation; too tight and the loop will not move.
If you want to play the loop for some time, then a more permanent way of holding the loop is called for. If the loop is fairly short and within the dimensions of the tape recorder then the rubber sucker off a child's bow and arrow set can be used. Place a pencil into the sucker and stick it down on the front facia of the machine, remembering not to apply too much tension to the tape. Once positioned properly this will allow you to play the loop continuously (Figure 3).
Medium length loops can be played with the aid of a bottle. Lie the tape recorder on its back, thread up the loop, place the loop around the bottle and tension the tape (Figure 4). Loops of a reasonable length can be played using this method. Longer loops need to be played using microphone stands to guide the tape (Figure 5), which should be placed so that there is an equal amount of tape between each one. This will help you to apply a similar tension to each section of tape and therefore help it to run more smoothly.
An extension of the loop idea is to use two tape recorders; the loop is used in the same way (Figure 6), and will allow you to playback the sound at two different points and mix them together. This is also a useful way of producing echo, but to do this you must put one of the tape recorders into the record mode, (see the article on tape echo techniques in the February issue of HSR).
With all of the methods outlined above, you should make sure that the objects the tape is in contact with are smooth and provide an easy path. They also should not be made from a metal with magnetic properties, as this could well degrade the sound quality after a period of time. Loops should be stored in dry, spacious containers, and should be marked with the tape direction, speed and name, using a chinagraph pencil, normally near the splice point.
The methods so far covered have dealt solely with open spool tape. You can, however, buy cassette loops, which are readymade and are sold in a variety of lengths. TDK make three lengths of durations 1, 3 and 6 minute tapes. Philips make a greater variety and Tandy make a 30 second loop. These tapes are difficult to get hold of but you may find them in good Hi-Fi shops, particularly the ones that sell home recording equipment.
There are two other types of loops which we have not discussed, cartridge player loops and the Revox loops. Both of these are almost never seen in the public eye; cartridges died a death nearly a decade ago and are now generally only found in radio stations where they are used for jingles, and Revox loops were discontinued in the mid-1970s.
With the coming of high quality, low cost digital delay units, many of the creative possibilities of short loops are now possible. Those delays which incorporate a 'freeze' switch can be used to store a sound and play it back just like a loop. At present times up to 4-5 seconds are available on units costing less than £1000. Editing is very crude and few have a reverse capability, though they do have the added advantage of pitch modulation. No doubt as technology advances, such operations will become 'childs' play' on a digital delay.
Feature by Paul Gilby
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