Let us take you into the world of the sharp piece of metal, and the sticky piece of paper. Martin Sheehan runs over the essential points of tape editing — what 'real' engineers do with razor blades.

IT MAY seem a touch primitive, but the razor blade is one of the indispensable tools of the audio engineering trade. In contrast, you can take a stroll around a posh video editing suite and see all manner of winking lights and wavering joysticks but the sharpest thing in sight is likely to be the agency man's suit.

This smooth edged approach is very trendy and technical, and it needs to be. Video tape and digital audio don't lend themselves to the simple splice. Analogue audio tape and film have more in common with each other in terms of editing, both requiring something sharp and something sticky. This cut and stick technique, basic as it may seem, is the correct and professional way of doing things when editing in this media. It is also cheap.

A digital editing system for audio or video will cost thousands, but providing you already have an appropriate tape recorder, you can kit yourself out for editing audio tape for under £20. The term "appropriate tape recorder" is rather sweeping but can be defined a little better as "any machine which allows you to get at the tape while it is in contact with the playback head". Unfortunately, this would tend to discount cassette machines, although a certain amount of cassette tape editing is possible albeit with a lesser degree of accuracy.

The ideal tape deck on which to edit is the stereo half-track reel to reel. The term 'half-track' refers to the fact that each channel of the stereo occupies one half of the tape width. The more common domestic machine is the stereo quarter-track which allows the tape to be used in both directions. The tape width in this case is taken up by two stereo pairs of channels with each track occupying a quarter of the tape width. Edits on a quarter track machine are just as effective as those on a half-track machine, but if there is any wanted material on the other side (direction) of the tape, be sure to copy it before getting stuck in with the razor blade.

Tape editing is a relatively inexpensive sport and the increase in quality from small items such as leader and splicing tape makes skimping not a worthwhile pursuit. Therefore the items to be found in the be-a-Junior-Editor-kit are much the same as those in the cutting-up-bits-of-tape-for-a-living-kit. The major item in both is the edit block. Editall market a very nice range of these, and the ¼in version can set you back about £20. However, there is a version known as Emitape which can do the job just as well, and will give you change from a fiver. Also required are single edged razor blades (about 65p for five), Chinagraph pencil (30p each), splicing tape (£1.50 for lots), leader tape (approx £4.00 for 250m — which may sound more than you'll ever need but it really is false economy to buy the tiddley lengths sold in Hi-Fi stores) and, of course, an empty reel or two.

Armed with the correct equipment, the correct technique can be sought — joining two pieces of tape so they stay joined, without sounding as though they have been. For practice, we'll kick off by putting a leader at the beginning.

Leader is the same size and shape as recording tape but has a distinctly different property — you can't record on it. It's not in the least bit magnetic, so produces a deafening silence. Consequently you'll find it at the beginning and end of songs, and often between tracks, guaranteeing noiseless intros and providing a visual indicator due to it being available in an array of pretty colours.

Run the tape up to the first beat or note of the song. This will put those immortal words "tape rolling" or "one, two, three..." by the playback head. As the first beat of the song is heard, press the pause button (edit on some machines). This should leave the tape in contact with the playback head, but not moving. Now gently slide the tape backwards and forwards across the head by rocking the reels — you'll hear the start of your recording as a slowed down rumble, and that will help you zero in on the beginning of the song.

Headphones are useful here to help catch the very low level start of a sound. They can also save embarrassment as a bass drum beat, passed slowly across a playback head and amplified through large speakers, can sound uncommonly akin to the relief of flatulence. Having wrestled with the spools to a point where the song is just about to begin, take up the Chinagraph pencil and mark, aiming the pencil at the apex of the playback head in order to be as accurate as possible. Some engineers then like to draw a line backwards along the section of tape they want to save, in order to identify it. If you are new to this game then it's advisable to re-run the tape through, press pause, and rock the spools again just to check that your mark still agrees with your ears. You can quite confidently go ahead and cut the tape if the mark lines up twice in a row — the only thing that could now be wrong is that you've aimed your Chinagraph at the wrong head! Whether your machine has two or three heads, the playback will always be the one nearest the take-up spool.

To cut the tape it must be placed in the edit block with the magnetic side down (ie the side that faced you as you were rolling the tape past the head still faces you as the tape is pushed down in the block). Try to place the block as near the head as possible to avoid unreeling too much tape to supply the necessary slack.

The block itself is made of a non magnetic, aluminium alloy and has an accurately milled, concave channel with a lip on each edge which is designed to hold the tape firmly, but release it without damage when pulled free.

There are three slots provided for your pleasure at angles of 45, 60 and 90 degrees to the tape path (more later). But it is worth mentioning at this point that you should never throw away any editing outakes until the edit has been played back and proved successful. Even the most experienced engineer is not infallible when it comes to remembering on which side of the marked edit point the wanted material lies. As long as no section of the tape has been irretrievably discarded, it's possible to remake a wrongly positioned edit and start again.

Provided there is no unwanted noise immediately before the start of the song, position the tape so that the chinagraph mark is fractionally to the left of the 45 degree slot. Cut through the tape with a single, steady stroke, holding the razor blade at an angle of about 30 degrees. Don't hold it flat and thrust it down into the slot, that will kink the tape and produce a bad cut.

If a red goo starts appearing on the floor, you've used your old double-edged Gilette rather than a single edged blade. Inadvisable.

Remove the two sections carefully, place some leader in the block and cut that at 45 degrees. Reintroduce the recording tape (the desired bit) from the left, and butt it against the leader. Cut just under an inch of splicing tape and run it lengthways along the join, pressing carefully but firmly to expel any air bubbles. Carry it on the edge of the razor blade to stop it catching on your jersey. Splicing tape is fractionally narrower than recording tape, so it can make a join without peeping over the edges where it could come into contact with the heads. You have to do your bit by laying it as straight as possible.

"Cutting and sticking bits of tape can be a cheap way to imitate some effects that are more commonly produced by expensive gadgetry."

It's also important that the ends of the recording tape and leader should butt neatly — an overlap will run roughly over the heads and peel apart, a gap will allow the splicing tape to show through and drop its sticky onto the heads.

About two yards is a pleasant length of leader for the beginning of a tape. It really doesn't matter what colour of leader you use but convention tends towards green at the start, red at the end and white for any spacing in the middle.

Splicing leaders is good practise for tape editing but the fun really starts when you get into chopping the things about which lie between them. Anyone who is working on four and eight track recordings, and is advanced enough to find themselves limited, can get a great deal more into a mix if they are handy with a razor blade. This applies equally to cassette based multi-trackers who can lay their hands on an open-reel machine for mastering. Working with a limited number of tracks increases the need for tight drop-ins. For example, the lead vocal and solo instrument may be on the same track — as the vocals finish on the second chorus and the guitar solo comes in for the third verse, a number of level EQ, and effects changes may be necessary all at once. Rather than calling in Uncle Tom Cobbly to lend extra hands, the mix can be done in sections and then edited together.

Taking the case above as an example, the mix can be taken as far as the solo or right through to the end of the song if the settings required after the solo are similar to those before, and the changes for the third verse can be ignored. Rewind the multi-track; make level, EQ and effects alterations and then master the third verse from just before its start to just after its end. Now the first beat of the amended third verse must be identified. Bass drum beats are often convenient points at which to edit. Their characteristic squelch soon becomes recognisable as the tape spools are rocked back and forth — don't forget, though, that even a percussive sound takes a little time to reach full volume and the leading edge is a very important part of the sound, so take care not to chop it off. Having located the first beat of the third verse, mark it and then run through and mark the first beat after the end of the third verse. Now mark the same two points on the mix with the duff third verse and splice in the new one.

If you make a mistake, the unwanted edit must first be peeled apart gently, starting by lifting one of the corners of the splicing tape NOT the recording tape. Now peel it right away and repeat the process with the other half. Although it can be tempting to leave one portion of the edit intact because only the other side is incorrect, this makes the rejudging and butting of the new edit a hit and miss affair. Better to splice all the bits of tape back in their original position, check it, then start afresh.

When editing in among the crotchets and quavers of a piece of music, the 90 degree slot in the edit block should be employed.

Although this doesn't allow such a strong join in the tape, a more accurate cut is possible. Also any cut other than one perpendicular to the direction of tape travel causes the edit to occur at a slightly different place on each track of a stereo tape, and that may cause a hiccup in the stereo imaging.

Another advantage of mixing in sections is that the length and format of a song can be changed without resorting to re-recording the original multi-track. Similarly the best chorus can be mastered more than once and inserted in place of any which don't come up to scratch. Different intros can be tried by pilfering any part of the song and sticking it on the beginning. However, a point to watch (or listen) for when chopping sections around is the reverberation tail and the possible premature curtailment of sustained notes.

When mixing in sections with the intention of creating a patch-work master it will often be the case that more than one section of tape will be disembodied from its reel at any one time. A simple way to help keep track of these temporarily liberated entities is to line them up in order over the back of a chair (or anything else non-metal-lic). In order to tell which end is which, it helps to chinagraph across half the width of the tape only. If you always stick to marking the same half, you will always be able to tell which way round the tape should go.

When editing the spoken word it's normal to use the 60 degree slot on the edit block. Although when we speak some words run straight into each other without a break, there is generally a little more leeway when editing between words than between beats in music. This, coupled with the fact that a commentary is likely to be in mono, allows us to use the 60 degree cut which can result in a smoother travel of tape over tape heads.

From the point of view of editing, tape speed is a very important factor. Because standard tape speeds increase as multiples of themselves (i.e. 1⅞, 3¾, 7½, 15, 30 inches per second), it's clear that each drop in tape speed halves the available editing space, or doubles the degree of error, whichever way you care to look at it. So it's always advisable to use the highest tape speed available on the machine if any editing is anticipated.

Cutting and sticking bits of tape can be a cheap way to imitate some effects that are more commonly produced by expensive gadgetry. The re-triggering effect often produced using digital samplers can be achieved by recording the appropriate word, phrase or chord a few times onto the mastering machine and then chopping out and sticking together the required bits. This edited piece of sampler-like tape can then be dubbed from the mastering machine back onto the multi-track in the appropriate place. The easiest way to keep the timing right when finding editing points for this sort of effect, is to actually measure the length of tape required for the total phrase and then make sure that all the little sections of tape are cut to lengths which are sub divisions of this total. In this way, when spinning the edited effect back from the master onto the multi-track, if you can get it to start in the right place it has to finish in the right place.

Tape loops are another useful little tool made possible by cutting and sticking tape. The loop is created by cutting out a section of tape and sticking its nose to its bottom. Within reason the length of the loop is variable between a minimum dictated by the distance around the tape head block and a maximum dictated by the distance across the room in which you are recording. The loop is played by threading it across the tape heads and between the capstan and pinch wheel in the normal manner. The tape guides should then be fixed with sticky tape to their normal playing positions. This is necessary to activate the micro switch which normally cuts out the motors when the tape runs out. With the tape deck on its back the excess tape can now be tensioned around something smooth such as a wine bottle, or if longer distances are involved, a mike stand. If resorting to a mike stand, however, try to avoid the tape touching any of the metal work and causing any possible magnetic whoopsees. The art of good tape loop reproduction is in optimising the positioning of the tensioning object. Typical uses for tape loops would be for sound effects such as wind and rain, or for repeating rhythmic backings. With sound effects such as the aforementioned, the edit point needs to be carefully chosen so as to avoid sounding obvious. The 45 degree slot on the edit block will help in this respect. When using tape loops for backing rhythms, however, it is the cyclic effect of the sound of the edit point which can be all important so the 90 degree edit can work here.

So, primitive as the razor may seem, it is a useful little fellow. And as that fateful day looms ever closer when the sky will open up and smother us in noughts and ones, we who have lived by the blade shall mourn its passing and look on helpless as the whole universe goes digital.