Here is a technical explanation of the delay system as explained by Robert Fripp to audience members

at most Frippertronics events as heard on numerous recordings. 

This is a delay system and not a tape “loop” (as in a loop of tape) as is often presumed.


Part 1 - How is a monophonic Frippertronics piece created ?


There are two Revox tape recorders placed at a variable distance apart.

The Left Revox has a tape spool on the left reel and the right Revox has an empty spool on the right reel.

The tape is fed from the Left Revox past it’s Playback head, then Recording head,

then into the Right Revox past it’s Playback head, then Recording head

and then collected in the empty spool of the Right Revox on the right reel.

Fripp’s guitar is fed through his pedal devices, directly into the Left Revox

and recorded on the Left Channel onto the moving tape.

The recorded guitar sound travels along the tape into the Right Revox past it’s Playback head.

The signal is fed via cable from the Right Revox Left channel back into the Left Channel of the Left Revox.

The mono signal is also fed from the Left Channel from the Left Revox into the PA system.

This typically creates about a 3 to 5 second delay from when a sound is made and before it is heard again.

This time varies depending on the physical distance between the two Revoxes and the tape speed.

The entire piece is captured in mono on the left channel only in the right reel of the Right Revox.


Fripp is able to bypass the signal path via footswitch, which allows himself to solo to the monophonic loop,

but rarely does so, as the delay system does not receive any additional sounds and simply continues to

decay in volume (i.e. uneventful).


Part 2 - How is a stereophonic Frippertronics piece created ?


The monophonic “left channel only” piece (created in Part 1) is rewound back to the start,

back onto the Left reel of the Left Revox.

The tape is played back by the Left Revox Left Channel and also recorded onto the Right Channel of the Left Revox.

This creates a true stereo signal because the Right Channel is one tape generation down from the original

version on the Left Channel and thus it’s EQ characteristics are slightly altered.

More importantly there is a delay of about 175ms between the Left and the Right Channel due to the

physical distance between the Playback and Record Heads of the Left Revox.

This has a separate and very distinct delay effect that gives the illusion

that the guitar sounds are “flying past your head”.

The tape travels to the Right Revox where it is played back to the audience in stereo through

the PA system and also again collected (this time in stereo) on the Right reel of the Right Revox.

As this requires no additional effort on Fripp’s part once he sets the Revoxes in motion,

he is free to add the additional element of playing solo guitar with the now stereo Frippertronics piece.

The stereo Frippertronics piece is changing in the identical manner in which he created it in Part 1

and therefore does NOT remain static (i.e. eventful)


The tape reel collected at this point is what we hear when we listen to God Save the Queen or Let The Power Fall.

Sadly this is captured WITHOUT the soloing element which is necessarily always external to the delay system.


Here is a short graphic display of the piece “1984” from the Let The Power Fall album.

The Blue wave pattern is the Left Channel and The Red wave pattern is the Right Channel.


The first view is from farther out showing about 15 seconds of the piece.


The second view is a close up of the first 1100ms of the piece.

Note the delay time between the left and right channels.


A variation of this stereophonic Frippertronics loop was discovered in the DGM Live releases

of the Frippertronics performances during his residencies held at

Washington Square Church and Inroads in New York City.

These took place from July 27 through to August 7, 1981.


At first it was believed that it had been synced up artificially in a different manner,

but upon close analysis and some careful attention to possibilities of the signal path

we believe we know how this was accomplished by Fripp at the event.


Here is an attempt at a technical analysis ...


“Normally” when creating a “stereo version” of one of these “mono creation reels”,

the tape was played back through the Left Revox, recording the left channel onto the right channel.

This is described in detail at the top of this page.

However this was NOT the case during these performances.


Fripp must have employed a signal splitter in addition to the normal “monophonic” loop creation technique

which would have taken the monophonic signal from the Right Revox Left Channel,

split it into two monophonic signals, one feeding back into the Left Channel of the Left Revox

as well as the Right Channel of the Left Revox.

This would have instantly created in real time the stereo loop we hear now.


At this point, Robert must have rewound the tape entirely onto the Left Revox

and used it as a conventional stereo playback Revox with two reels and played back the tape

through the PA and collected the tape on the right reel of the Left Revox.


The right Revox could have then be used to have recorded Fripp’s direct “solo guitar element”

in mono on a separate reel like a normal Revox recorder.

This is why Alex Mundy at DGM was only able to barely hear the sound of the backing loop

via the only connected “recording microphone” present … Fripp’s guitar pickups !

Or Fripp simply brought a 3rd Revox to these shows to record the solo elements separately.


Other technical notations …


At various times, usually at the beginning of some of these loops performed,

Fripp would mute the signal path running from the Right Revox back to the Left Revox,

which would effectively prevent repetitions.

It is unknown whether this was intentional or accidental.

We believe it was intentional as it occurred more than once

and created some interesting openings to a number of these pieces.


Also occasionally there were a number of times where

the signal splitter did not function properly and would cause

sections where the right channel signal was missing.

This is likely due to Fripp forgetting to engage the signal splitter for the first minute

or perhaps it somehow was subsequently erased in error.


Fripp also may have used a differently modified Revox during

some/all of these 1981 performances in NYC as it appears

he was able to somehow accomplish a 500 ms left vs. right channel delay

which is about 3 times as long as the standard Frippertronics delay.


Below is a graphic detail of this unique Frippertronics loop

for comparison against a “normal” Frippertronics stereo loop as seen here

First a far view 27 seconds and a close up view (6 seconds) showing NO left/right channel mini-delay

with the absolutely PERFECTLY synced 4-5 second delay.



The second view is a close up of the first 1100ms of the piece.

Note the perfect synchronization between the left and right channels.


Click here for more information on the technical mechanics of the A77 Revox Tape Recorders.