How to make an evolving tape loop

What is a tape loop?

A tape loop is a short phrase recorded and joined end to end so it plays over and over. The name is literal. In the 1960s you made one from a length of magnetic tape spliced into a physical ring, often run out around a mic stand or a pencil to keep it taut, so the same few seconds passed the playhead again and again.

The classic technique is not just to loop a phrase, but to let it change while it loops. You record something short, set it running, and let the tape wear out. As it ages and passes the head hundreds of times it loses top end, drifts in pitch, sheds a little of its coating and picks up noise, so the loop you started with slowly turns into a different one.

Two records made this famous. William Basinski's The Disintegration Loops is the sound of tape loops he had made decades earlier physically crumbling as he tried to digitise them, each pass shedding a little more of the recording until the music decays to almost nothing. In the 1970s Robert Fripp and Brian Eno used long tape delays built from two reel to reel machines, feeding a phrase back on itself so it layered and changed over minutes. Fripp kept using that setup for years and it became known as Frippertronics. Different machines, one idea: a loop that refuses to sit still.

How do you make loops that never quite repeat?

Layer several loops of different lengths. If every loop is the same length they lock together and you hear the same seam on every pass. Make them different lengths and they drift out of phase, so the combination lands in a slightly new place each time and takes a long while to come back round, if it ever does.

This is the oldest tape loop trick there is. One loop four seconds long, another seven, another eleven, none of them a neat multiple of the others. Each is simple on its own. Together they cross and overlap in a pattern that does not repeat for minutes, because the moment where all three line up again is a long way off. Longer and stranger lengths drift for longer.

The lengths matter more than the notes. Pick a single chord or one scale so nothing can clash, then let the phasing do the composing for you. This drift is the same engine that powers slow generative music, which we pull apart in how to make generative ambient that plays itself: layers of different lengths that never sync.

How do you make a loop wear out over time?

Add tape damage, and turn it up slowly as the loop plays. Wow and flutter, saturation, dropout and a filter that closes a little more on each pass, all sitting under a long reverb. The trick is that these should increase over time, so the loop sounds fine at the start and audibly tired by the end, the way a real tape does after a hundred passes.

• Wow and flutter. Slow pitch drift and a faster shimmer, both from the tape running at an uneven speed. A little makes the loop feel unsteady in a good way. Too much and it reads as broken.
• Saturation. Gentle overdrive that thickens the sound and rounds off the peaks at low levels, and turns to grit as you push it. Let it creep up as the loop ages.
• Dropout. Brief dips in level where the tape has shed its coating. Occasional and slightly random early on, more frequent as the piece goes.
• Filtering. Roll the top end down slowly across the whole piece so it grows darker and more distant, like a recording heard through more and more tape.
• Long reverb. A large, long reverb over everything. As the loop thins out and loses detail, the reverb tail is what is left holding it together.

For what each of these actually is, and how much is realistic before it stops sounding like tape and starts sounding faulty, see wow, flutter and saturation: how the tape sound works. The one rule that matters here is to automate them upward. A loop that is equally degraded from bar one is just a dirty loop. A loop that starts clean and comes apart has an arc.

How do you turn it into a finished piece?

Let it run, record a long single pass, and keep the stretch where the wear has turned the loop into something new. You are not editing every bar. You set the system going, leave it, and choose the window where it has travelled furthest from where it began.

Because the loops are different lengths and the damage is rising, the interesting section is almost never the start. Give it time. Somewhere a few minutes in, the phasing has moved the parts somewhere you would not have written, the top end has gone, dropouts are opening holes in it, and the reverb has swallowed the edges. That is the piece. Record a long pass so you have room to go and find it.

Then know when to stop adding. The temptation, once it is running, is to play something over the top or bring in a second idea. Resist it. The loop wearing out is the composition, and a fixed new part just gives the ear something solid to hold, which is the opposite of what a dissolving loop is for. Let it thin to almost nothing and end it there.