$Page PitchLoop89
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*Welcome to PitchLoop89*

PitchLoop89 is a new pitch-shifting device inspired by the Publison DHM 89, created in collaboration with Robert Henke. Experiment with jittery glitch effects, delayed digital shimmers and outlandish vibrato in the studio or onstage. 

The device contains two independent pitch-shifting delays. Pitch shifting is achieved by using the digital equivalent of a tape loop with one head for recording and two moving heads for playback. Only a portion of time is played back, and then the delay jumps back to the beginning of the segment. The position and movement of these virtual playback heads define the sonic character of the pitch shifting and the overall delay.

The implementation of this principle in PitchLoop89 adds a lot to this basic concept, and turns it into a flexible sound design and performance tool.

$Page Global_Functions

*Global Functions*

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The two pitch-shifting units can be operated independently, or together as one stereo effect, by activating the *Link* control.

A global *Bandwidth* control defines the recording and playback sample rate. This affects the maximum delay length, momentary values for playback controls and for the upper frequency limit of the processing (20kHz, 10kHz, 5kHz). In the 20kHz setting the un-pitched delay line has a length of two seconds per channel.

The historical reason for this parameter was limited RAM in the hardware. This is not an issue today, but since switching the sample rate creates interesting results the function is also implemented here. 

The content of each channel can be 'frozen' using the *Hold* control. What you hear in that mode is a (crossfaded) loop set by the *Position* and *Segment* parameters. In both normal and frozen modes the segment can be played backwards using the *Back* toggle. To make it simple to work with shorter rhythmical delays, A *Short* function is also available. 

Just like the hardware it is inspired by, PitchLoop89 allows you to do 'signal informed crossfades' between segments. This is done when *Xing* is active. In this mode, the device finds the best possible transition point for pitched signals. Usually the fade between segments is quite short, but for some materials a longer fade is desirable, which can be enabled using *Fade.* 

$Page Pitch_Shifting

*Pitch-Shifting*

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Pitch shifting has a range of -24 to +24 semitones, and is controlled using the *Pitch* parameter. *Fine* allows for tuning continuously in a range of +/-1 semitone. Pitch shifting will directly affect the sound, and is strongly dependent on the values of Segment, Xing, and Fade.

*Vibrato* can be added using a dedicated LFO with a choice of a bipolar sine wave or unipolar (upwards only) square wave, with a range of up to 12 semitones. The resulting pitch, including the effect of the vibrato LFO, is shown in a numerical display.


$Page Delays_Position

*Delays and Position*

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The distance between the virtual record head and the playback unit is defined with the Position parameter, but since the pitch shifting playback has to be done in short slices, a second parameter, *Segment,* defines the length of each slice. Segments with short durations sound very different to longer ones, and the perceived quality of the pitch shifting depends largely on the segment size. 

Small settings are typically more useful for pitching rhythmic material, while long settings might work best for textures.

$Page LFO_Display

*Position LFO and Display*

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The position of each slice can be modulated with two different sources: *Random* and *LFO.* Small random values slightly 'smear' the signal, which might sound more natural, while larger settings have a more granular effect. 

The LFO offers plenty of waveforms including Move – a smooth random movement. Its effect is highly dependent on the settings of the other parameters, and all sorts of oddities can be achieved, ranging from subtle to drastic. When *Hold* is active, the device acts like a looping sampler where Position defines the start point, and Segment sets the loop length. LFO and position modulation can be used for rough time stretching or wavetable-like effects. 

When Hold is inactive, it is possible to momentarily warp incoming material. The center bar graph and numerical displays show the current position, including modulation and corrections, allowing for click-free playback.

When changing pitch or using Fade, corrections which lead to longer minimum delays can be drastic. You can also observe fluctuations in delay time when Xing is enabled.

$Page Filtering_Feedback

*Filtering and Feedback*

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The output of each delay line is processed with two filters, a low cut (or high pass) filter, and a high cut (low pass) filter. They can be vital for shaping the sound and they are located inside the feedback path, so they are applied recursively when feedback happens.

The *Feedback* parameter re-routes the output signal of the pitch shifter back to the input, and the destination is defined by the chosen routing option:

*L/R* means each pitch shifter feeds back to its own input. This makes them completely independent. 

*Sum* combines both feedback signals and sends them back to both inputs. 

*Cross* routes the signal from the left channel to the input of the right one and vice versa. 

These routing options allow you to create complex cascades of pitched feedback. 

Each pitch shifter also has its own *Output* level control and both share a common stereo parameter.

$Page Credits

*Historical Background*

PitchLoop89 is partially inspired by the *DHM 89 B2* pitch-shifting delay unit, made in 1978 by the French company *Publison.* It does an amazing job with very limited hardware – it doesn’t even have a CPU, all functions are carried out with a mix of analog VCAs, logic gates, counters, tons of TTL chips, TL071 OpAmps and 4066 CMOS analog switches. 

It came with an additional unit, the *KB 2000,* which allowed you to play on a keyboard, with added features like time-stretch playback. At the time this was quite ground-breaking and used extensively by the composers at INA/GRM and many others. Some of the most beautiful features are a byproduct of the technology, like the octave jumps when switching sample rate/memory time. 

I wanted to port the essence of it into a plugin, and while doing so I came up with a lot of new ideas. The resulting device offers several options not available in the original hardware. And, of course, you can use multiple instances without the need to sell your house to afford it. You also don’t have to worry about it breaking, and then not being able to find someone to repair it. 

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*Credits*

PitchLoop89 was developed by Robert Henke. 

User Interface design by Eric Carl @ Ableton together with Robert Henke.
 
Special thank you to Jonathan Prager for making sure my original hardware DHM 89 is working fine :-)

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Visit Robert's homepage here:
$Link RobertHenke.com<https://roberthenke.com/>

For more Packs from Robert, please check here:
$Link www.ableton.com/en/packs/by/robert-henke-monolake/<https://www.ableton.com/en/packs/by/robert-henke-monolake/>

More Packs available here:
$Link www.ableton.com/packs<http://www.ableton.com/packs>

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