The Hi Fli (aka The Sound Freak) was designed by David Cockerell in 1971 for EMS. He later went on to design many of the classic Electro Harmonix effects (both the Micro Synth and Small Stone phaser are inspired by the Hi Fli). Only 350 were made making it a collectorâ€™s gem. David Gilmour bought a prototype in 1972 and from what he recalls it was â€œvery, very expensiveâ€.
The Hi Fli was actually referred to as a synthesizer in the original ad, but itâ€™s basically an analog multi effect processor, which can be used on vocals, guitars and organs. It has two footpedals, which could be routed as control voltages/expression pedal to any of the slider functions. Itâ€™s got no memory to bank up settings, – everything is in real time, so one had to manually tweak the sliders for each tone change.
Top Boost: Provides up to 30 db treble boost.
Octave Shift: Drops the pitch by an octave.
Buzz Switch: Adds high frequencies overtones to the sub-octave signal.
Ring Mod: Produce an octave higher when a signle note is played and the typical ring modulation when two or more strings are played.
Decay Rate: A rotary control controls the decay time of the ring mod and octave shift signal level.
Sustain Fuzz: Special circuits detect the beginning and end of each note and apply upper harmonics.
Attack Rate: A rotary control varies the rise time of Sustained Fuzz signal. Notes can be sustained even though the original signal has dropped by more than 20db.
Pedal Switches: The switches under the sliders combine the pedal control with the manual sliders. Selections of switches with pre-set slider positions enable the pedal to change treatments instantly.
Solo/Strum: This switch alters the Hi-Fli’s sensitivity to signal attacks and should be set to more sensitive for single notes (i.e solo).
Bypass Mix Fader: This central slider controls the mix of the original and treated sound. In the high position only the input pre-amplifier is in-circuit. The bypass footswitch gives instant access to this position. The output from the Octave shitft, Ring Modulator and Fuzz Sustain sections are re-combined and go to the phase filter and modulator section.
Control Modulation Selector: 6 position control knob.
Treatment Selector: There are six distinct modes of operation – Vibrato, two modes of Phasing, normal WAA-WAA (1 resonant peak), WAW-WAW (six resonant peaks) a completely new sound, and finally MEOW (two sets of three resonant peaks moving in oppisite directions.
Modulation Speed: This slider operates in the first 4 positions of the control modulation selector, providing a fine frequency control.
Modulation Ramp Time: Operates in positions 3 to 6 of the conrol modulation selector.
Modulation Depth: Controls the depth of the Phaser.
Frequency shift: This controls the frequency domain in which the modulation waveform operates, being central for symmetrical modulation.
L.E.D selectors: Two light emitting diodes show the movement of the modulation waveform.
It’s not documented when David got/bought the Hi Fli but assumably sometime medio 1972 as it was featured on the Dark Side of the Moon recording sessions. The Hi Fli was also featured in David’s rig during the brief US tour in March 1972 and at Earlâ€™s Court, London in May 1973. Itâ€™s not documented which songs he used it on, but it might have been for creating auto wah effects on Any Colour You Like and fuzz on live versions of Time.
The Hi Fli is still in Davidâ€™s possession and was last seen at the Interstellar Exhibition in Paris in 2003/04.
Information gathered from ems-synthi.demon.co.uk, â€œAnalogManâ€™s Guide to Vintage Effectsâ€ by Tom Hughes and the David Gilmour Gear Forum, post written by HiFli owner â€œRichardâ€.