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Delia Derbyshire and the art of tape

September 21, 2026

Written by Jordan Elias, MT-BC

In the early 1960s, inside a converted building near the BBC's Maida Vale studios, a composer built music entirely by hand: cutting quarter-inch tape with a razor blade, splicing it back together in a different order, playing loops at speeds no instrument could produce, and multiplying one signal against another until neither retained its original pitch. This is a browser recreation of some of her core techniques. Record or upload a short clip onto each of the four tracks below, then shape it with speed, filtering, ring modulation, and a slow LFO. When you're happy with the layers, render the mix and download it.

Splice, splice, splice

Before synthesisers were commercially available, the primary tool of electronic composition was a razor blade and a roll of splicing tape. Sounds were recorded onto magnetic tape, then physically cut apart and reassembled: a note extended by repeating a section, a rhythm built by cutting silence out between hits, a phrase reversed by turning the spliced segment around before taping it back in. Derbyshire worked this way for entire pieces, sometimes spending a full day of cutting to produce a few seconds of finished material.

Every cut was a compositional decision. There was no undo, no non-destructive editing, no waveform view to zoom into. Only the sound of the tape itself, judged by ear and by ruler, marked in pencil, and cut roughly on a diagonal to avoid an audible click at the splice point. The physical resistance of the medium was part of the aesthetic: because editing was slow and consequential, each decision about structure was made deliberately.

Varispeed: the tape machine as instrument

The other central technique was varispeed, or running a tape recorder faster or slower than its standard speed. Because pitch and playback speed are physically linked on a tape machine, halving the speed drops a recording exactly one octave, and doubling it raises one octave; smaller speed changes produce smaller, less familiar intervals. Derbyshire used this constantly, recording a single source and creating an entire register of pitched material from it by re-recording it at different tape speeds.

In the tool above, the speed control on each track works the same way: it changes playback rate and pitch together, exactly as a real tape deck would, rather than correcting pitch to keep it separate from tempo the way modern software often does by default. The interval readout beneath each slider shows you how that speed change affects the pitch, speeding up an octave, slowing down by a fifth, and so on.

The Doctor Who theme, built in pieces

Derbyshire's best-known realisation is the 1963 Doctor Who theme, composed from Ron Grainer's short sketch. She began with recording individual notes one at a time onto tape. Plucked strings, oscillator tones, or white noise were then cut apart, transposed to the pitch she needed using varispeed, and reassembled on a fresh reel: a bass line built from a series of transposed and cut fragments, a melody built the same way, each layered on top of the last by recording from one tape machine onto another. What sounds, in the finished piece, like a single continuous electronic performance was in fact one short recorded source, transformed multiple times and layered.

Grainer reportedly asked, on hearing the result, "Did I write that?" — to which Derbyshire is said to have replied, "Most of it." She received no composer credit for the work; BBC policy at the time held that Radiophonic Workshop staff produced sound effects, not compositions.

Ring modulation and the Delian mode

Alongside tape editing, Derbyshire made extensive use of the Workshop's ring modulator. Ring mod is a circuit that multiplies two audio signals together rather than mixing them. The output of true ring multiplication contains only the sum and difference of the two input frequencies, and none of the original tones: a 220 Hz sound multiplied against a 150 Hz carrier produces 370 Hz and 70 Hz, and nothing at 220 or 150 at all. This is the source of the metallic, faintly inharmonic quality that runs through much of her work. timbre with no equivalent among acoustic instruments, because it isn't built from harmonics at all.

Each track in the tool above has its own ring modulator, with a carrier frequency you can sweep, and a live readout of the resulting sum and difference tones. Try enabling it on a recording of your own voice and listen for the moment the sound stops resembling speech and starts resembling metal.

LFO: the wobble Derbyshire did by hand

An LFO — a low-frequency oscillator — is a signal moving too slowly to hear as a pitch in its own right, typically well under 20 cycles per second, used instead to gently push some other parameter up and down on a repeating cycle. Route it to volume and you get tremolo; to pitch, vibrato; to a filter's cutoff, a slow wah; to stereo position, a drifting pan. Almost every synthesiser built since the 1970s has one. Derbyshire had no such circuit for most of her time at the Workshop.

What she had instead was the flutter of the tape machine's own speed instability, and where she wanted something more deliberate, her own hand: nudging a speed control very slightly while a tape played, recording a physical vibrato performance directly, or riding a fader up and down by feel. It amounts to the same shape an LFO produces electronically — a slow, repeating push on some parameter — just applied one careful movement at a time rather than by circuit.

Each track above has one LFO, routable to four destinations: Filter, for a slow sweep in tone colour; Volume, for tremolo; Pan, for a drifting stereo position; or Ring, which wobbles the ring modulator's carrier frequency for an unstable, wavering metallic vibrato. A slow rate — under 1 Hz — routed to the filter gets closest to the feel of a hand easing a control back and forth.

Filtering, reverb, and the loop

The Workshop's other essential tool was a bank of filters, circuits that remove or emphasise particular frequency ranges. A lowpass filter lets the low end through and rolls the high end off, giving a muffled, distant character; a highpass does the opposite, thinning a sound down to its top edge; a bandpass keeps a narrow slice in the middle and removes both extremes, producing the telephone-like quality that runs through much of the Workshop's percussive noise. Each track above carries one of these three filter types, with a cutoff frequency and a resonance control that emphasises the frequencies right at the cutoff point.

Reverb is included for a more practical reason: once a fragment has been transformed past recognition, a little sense of space helps it sit inside a mix rather than floating disconnected from everything else. The loop and crossfade controls solve a more mundane, very real tape problem — looping a recording that wasn't recorded to loop seamlessly produces an audible click where the end meets the beginning again. Crossfading blends the last few milliseconds of the loop into the first few, the same way a tape editor would have made a diagonal splice.

Number as structure

Among the papers found after Derbyshire's death in 2001 were notebooks of grids and integer sequences — frequency ratios mapped to pitch, duration, and dynamics. She worked with serial methods, but not the twelve-tone technique of Schoenberg; her structures were built from simple whole-number ratios — 1:2:3:5:8, or 4:7:11:13 — used to determine the relationship between layers of sound, harmonic and otherwise. It was a way of building coherence out of arithmetic proportion rather than out of familiar scales.

The ratio panel above the tracks lets you try a version of this directly: set an integer ratio for each track relative to track 1, lock them together, and every track's speed, and therefore pitch, rescales proportionally as you adjust the first. Four identical layers of the same source material, related only by number, can produce a chord that has never existed as a scale.

Tape as material

It's worth noticing what made this way of working different from simply pressing "play". Every transformation Derbyshire applied to a sound: slowing it, cutting it, multiplying it against another signal changed what that sound fundamentally was, not just how it was arranged. The tape stopped being a way of storing a performance and became raw material.

There is a useful parallel here to any process of working something through by hand, slowly, with attention. Experiences, feelings, memories don't have to stay in the form they arrived in. Cut apart, slowed down, set beside something else, held at a different angle, they can become material for something new. Transformation while staying true to their origins.

Check out the earlier phase machine post exploring a related idea through Steve Reich's tape phasing.

Experiments

If this resonates

This is part of a series on sound, perception, and experimental music as therapeutic frameworks. Related posts: the phase machine and Steve Reich's tape drift, building rhythm with a step sequencer, and generative systems.

If you are curious about music therapy in practice, you can learn more about music therapy here. You can also book a free 30-minute consultation to discuss how music therapy could benefit you, with no commitments.

Further reading:

• Sisters with Transistors — documentary on women in early electronic music
• The Delia Derbyshire Archive, University of Manchester