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DigiTech IPS33 SmartShift

Intelligent Pitch Shifter

Most pitch shifters wouldn't know their A minor from their E major, but DigiTech's IPS33 knows a thing or two about playing in key. Simon Trask finds himself in harmony with the Intelligent Pitch Shifter.

In the present climate of sampling madness, a pitch-shifter can help you tailor a sampled drum break as well as harmonise your vocals. Why not try an intelligent pitch shifter?

SMART? INTELLIGENT? IS the IPS33 trying for membership of MENSA? Such words are open to misinterpretation when used to describe machines, not least because they're inevitably relative rather than absolute - today's intelligent machine will no doubt end up as tomorrow's dumb one.

What DigiTech are getting at is the fact that the IPS33 doesn't blindly pitch-shift at a fixed interval, as pitchshifters are traditionally wont to do, but in key. This means that the interval of, say, a third will be major or minor depending on what note you're playing and what key you're playing in. For instance, a third up from C in the key of C major is a major third (C-E), while a third up from E in C major is a minor third (E-G). What qualifies the IPS33 for its "intelligent" tag is the fact that it can distinguish the difference and output a pitch-shifted version of the source note appropriately. In fact, the unit can output two pitchshifted signals, independently definable, thus allowing you to produce all manner of three-note chords in conjunction with the input note. I should point out that the IPS33 requires a monophonic input to be able to successfully determine what shifted pitches to output; inputting chords or even overlapping notes can cause problems (more a "warbling" than any serious glitching) for the SmartShift, though it's more readily able to handle the more straightforward intervals - octaves, fourths and fifths. (As always, if you're of an experimental frame of mind you can play fool-the-technology).

For keyboard players this means it's best to select a monophonic performance mode if possible, but if not then sounds with an immediate or quick release should be used, and fingers should be picked up smartly (that's smart as in quick, not smart as in intelligent). If you're playing one of the growing number of synths which has onboard reverb, you should use it with care, as the resultant overlapping of notes will give the SmartShift pitching problems.

Another point worth making upfront is that you can't expect to use the IPS33 with any and every sound that takes your fancy (a temptation, when as a keyboard player you have so many sounds at your disposal). As with any pitch-shifter, there's a delay between the original signal and the pitch-shifted signals, something like a slapback echo in this case. It's particularly noticeable on "clean" sounds with a sharp attack, for instance slapped bass. Though it's often not what you want, with some sounds it can be a desirable effect. However, for the most part the IPS33 works best with thicker sounds with a slightly "diffused" attack stage. Ultimately the only way to find out what works and what doesn't is by experimenting. I tried a wide variety of synthesised and sampled sounds plus electric guitar, and even ventured to sing into it (harmonising a solo vocal line could become one the SmartShift's most popular uses). The IPS33 works best if the pitches input into it are in tune with its expectations; DigiTech have included a tuning function which gives you a visual display of whether you or your instruments are sharp, flat or spot on. However, I must say that the IPS33's ability to track fluctuations in pitch is very impressive, as is its ability to sharpen or flatten its shifted pitches by about a quarter tone before adjusting to the next semitone. Another very significant aspect of the IPS33 which makes it well worth investigating is the cleanness of its shifted output signals, a testimony to the power of digital signal processing.

Now, the IPS33 doesn't actually know what key you're playing in unless you tell it - it's not that clever. Shouting out a key change to it as you're playing won't do much good, either (one day, one day). Instead you program the key as part of a Preset memory, and then select the relevant Preset when you need to play in that key. Straightforward? Well, in practice it's not quite that simple, but it's not too difficult either.

Keeping Up Appearances

THE IPS33 ISN'T overburdened with parameters, but that's probably a good thing as it makes front-panel access straightforward. Twelve parameters are listed in a matrix format in the left half of the front panel, with associated pinpoint LEDs indicating the currently-selected parameter. Parameter display is taken care of by the central four-character LED window (no patch names here), while up/down buttons to the right of the window allow you to adjust the parameter values and two further buttons allow you to step vertically and horizontally around the parameter matrix.

In the right-hand half of the panel are three knobs which govern output level, output mix (of the input and shifted signals) and input level, with four Headroom LEDS (three green and one red) indicating the strength of the input signal. The optimum input level is indicated when the three green LEDs are alight but the red one is dimmed.

The IPS33 allows you to select line- or instrument-level input via a button located on the rear panel, where you will also find MIDI In, Out and Thru sockets, a Bypass footswitch input which allows you to switch the pitch-shift effect in and out, send and return effect sockets, audio input socket (which can accept balanced and unbalanced signals), and unshifted, harmony one/mono and harmony two output sockets. With the obvious exception of the MIDI sockets, these are all 1/4" jack sockets.

DigiTech have adopted a flexible audio output arrangement, whereby you can output the original signal for further processing, output all three signals via the harmony one/mono jack to a single amp or desk input (in which case you can control the mix of original and shifted signals using the output mix knob on the front panel, but not of the two shifted signals), or output all three signals via their own sockets to, say, three channels on a mixing desk. With the output mix knob turned all the way to the shifted signal, the unshifted signal will only appear at its own output: then you can control the level of and add further effects to each signal independently.

DigiTech have included the send/return loop for the purpose of inserting a distortion effect pedal into the signal path. This way, the IPS33 can control what is sent to the effect and what is pitch-shifted, which positioning the box either before or after the IPS33 obviously wouldn't allow.

"The IPS33 not only gives you enough harmonic flexibility to experiment - no matter how fast the key or chord changes, the unit can handle them if you can."

DigiTech claim their approach offers the warmest distortion effect, though this wasn't something I was able to try cut, being in a distortionless situation.

"Hidden" parameters accessed by combination button presses as you turn on the IPS33 allow you to see the software version number (the review model was v1.06), activate a self-test mode which will tell you if the unit is in tip-top shape or not, activate a display mode which repeatedly steps through the pinpoint LEDS and scrolls the name of the unit across the LED window (this is really intended for shops, but what the hell), and allows you to restore all 99 Presets to their original factory state (as this wipes out all your own Presets, be careful not to press the wrong combination of buttons when you turn on the SmartShift!).

Shifting Into Harmony

THE PS33 HAS 99 Preset RAM memories, each of which stores the information necessary to tell the unit what two harmonies to produce from any note you play. You're provided with a choice of 15 scales, as follows (deep breath, now): Chromatic, Major, Minor, Harmonic minor, Melodic minor ascending, Dorian, Mixolydian, Lydian, Lydian Augmented, Wholetone, Half-whole diminished, Whole-half diminished, Major pentatonic, Minor pentatonic and Blues. Wot, no Phrygian?

The Key parameter in fact selects the root note, while the scale type defines whether the key is major, minor or modal. You then select interval for each of the two shifted outputs relative to the input note, within the overall range of +/-1 octave. The number of possible intervals depends, of course, on the number of notes in the scale (in most cases this is seven excluding the octave, but the half-whole and whole-half scales have eight each, the pentatonic and blues scales have five each, and the chromatic scale, of course, has 12 notes).

The IPS33 works out what the actual intervals should be (ie. major, minor, perfect, augmented/diminished) depending on the chosen root-note and scale. The chromatic scale is the odd one out, in that the intervals are constant because the chromatic scale isn't in any particular key; consequently the root note is meaningless. In this instance the IPS33 behaves like a traditional pitch-shifter.

In all likelihood when you play a solo or a melody, the chances are you don't only play the notes of the key you're in. Passing notes, flattened notes, excursions into a different mode, all of these require some kind of "intelligent" action from the IPS33. How, for instance, should a fifth above F# be harmonised in the key of C major? DigiTech have considered such matters, and they've come up with the conclusion, quite rightly, that there's no one way to harmonise what they call an NST (non-scale tone). Thus they've provided five Variations, each of which provides a different harmonisation of the NSTs: diatonic, parallel, diminished, modal and altered. These make 59 scale types in all, with each scale and variation constituting one scale type (only 11 of the scales have multiple Variations; major and minor pentatonic and blues are diatonic, while the chromatic scale has no need of a Variation, as it has no NSTs).

With Diatonic selected, an NST generates the same notes as the scale tone below; with Parallel selected, an NST generates the same intervals as the scale tone below; with Diminished selected, each NST generates notes from a whole-half diminished scale, taking itself as the root of the scale; Modal treats an NST as the root of its own Lydian scale; and Altered treats an NST as the root of its own Mixolydian b2,b5,b6 scale. The best way to find out what results these Variations give is to experiment with them, as their effects vary greatly according to what scale and intervals you're using, but there's no doubt that having such a variety of ways of handling non-scale pitches greatly adds to the IPS33's harmonic possibilities.

But this isn't all the IPS33 has to offer. DigiTech have included 16 User Definable Harmonies. These allow you to define a pair of intervals (as with the other scales, up to +/ -1 octave each side of the source note) for each note in the chromatic scale. Unlike the other scale types, these intervals are not relative to any key - you define the key(s) by your choice of intervals (and therefore chords) for each note. The UDHs allow you to create more variety than the parallel motion of the other scale types can, being more akin to true arranging.

"There's a further use for pitch shifting - to bring samples off record/tape/CD/DAT into key and into tune without changing their tempo or length."

Unlike Preset editing, the changes you make to a UDH are saved automatically. UDHs can be selected as part of a Preset in place of one of the other scale types, with the associated root note of that Preset defining the start of the chromatic scale; in this way you can use the same UDH in different transpositions across up to 12 Presets.

Finally the IPS33 is able to use its two shifted outputs to produce detune effects, by shifting the input signal in cents rather than semitones; in this case (and only this case) the input can be polyphonic. You are offered a choice of 30 shift values for each Harmony (+/-15), referenced to one of four Detune "scale types". Detunes 2-4 multiply the intervals of Detune 1 by two, three and four respectively, with the maximum interval of Detune 4 being roughly a quarter-tone sharp or flat. The results can range from a very pleasant thickening of the input sound to a positively "honky-tonk" effect.

Sampling In Harmony

OF COURSE, AS any self-respecting sampler (person not instrument) will know, there's a further use for pitchshifting, namely to bring samples off record/tape/CD/ DAT into key and into tune without changing their tempo or length. Reconciling the tempi, pitches and keys of different samples can be a tricky business, where getting the tempi aligned might throw out both the tuning and the harmonisation. A pitch shifter allows you to reconcile the latter without affecting the former. Using the IPS33 you can adjust the pitch in semitone intervals using the Chromatic scale type, or fine-tune it using one of the four Detune options; unfortunately you can't do both at the same time, so if both are required you'll need to record the result of one treatment onto tape, resample it and then adjust it again (of course if your sampler can sample while playing back existing samples, you can cut out the tape stage and just resample). Having tried out the SmartShift with a variety of samples in this context, I can conclude that it functions very effectively (with the clean output of the transposed signal(s) being a definite plus point). And of course once you have a sample as you want it, you can use the IPS33 to detune (rather than fine-tune) it or play it back in three-part harmony.

The MIDI connection

NOWADAYS ANY EFFECTS processor worthy of the name must include MIDI in its calculations. The IPS33 is no exception, though its MIDI facilities are fairly straightforward. You can bulk transfer the IPS33's Presets and Harmony Definitions via MIDI SysEx, and set the unit to respond to patch changes on an individual MIDI channel (1-16) or on all channels (Omni mode). In this way you can call up IPS33 Presets from, say, a MIDI sequencer, the obvious use being to align patch changes (and therefore SmartShift Presets) with key changes and even chord changes in a song. Of course, first you need to plan what Presets you need and where you need to position them in your song. The extent of the task depends on the complexity of the chords and the number of key changes and/or chord changes. Getting everything in place can be laborious, and the jazzier harmonies can give you headaches (you try working out the right scale, NST variation and root note to program for a C7#5b9#9 chord), but in truth the task is as easy or as difficult as you want to make it (remember also that the 16 User Definable Harmonies allow you to program more sophisticated harmonisations than do the 15 scale types and their variations).

The IPS33 not only gives you enough harmonic flexibility to be able to experiment to your heart's content, but no matter how fast the key or chord changes are, the unit can handle them if you can. After testing the SmartShift over the changes of, among other things, Coltrane's 'Giant Steps' I can report that it holds up its end extremely well (which is probably more than can be said for yours truly). A strong point in the SmartShift's favour is the fact that, once the Preset changes are in place in your sequencer, you can forget about them and concentrate on your playing, because there's no glitching whenever the unit switches to a new Preset. You can hold a note through a Preset change and if the harmony notes need to change then they will, instantly and smoothly. Now that's what I call music the ears.


IN THESE budget multi-effects processors, the IPS33 might seem a trifle expensive - considering it only handles one type of effect. There again, pitch-shifting is not one of the easiest effects to accomplish, and often ends up being the poor relative in any multi-effects device which attempts it.

But it's really the IPS33's ability to pitch-shift in key which takes it into a different league. As far as I'm aware, the only other pitch-shifter which has the ability to harmonise in key is Eventide's H3000 Ultra-Harmonizer, which was debuted at last year's APRS show. This has a similar set of features to those of the IPS33, plus digital reverb, flanger, chorus, echo and EQ, and extensive MIDI control of its parameters. Both more comprehensive and more sophisticated than the IPS33, it also costs more than twice the price of the latter, which makes DigiTech's unit a budget alternative.

The IPS33 is very straightforward to operate, any complexities being more to do with working out what keys and scales to use in order to create the correct harmonisations. The slight but noticeable inherent delay between the unshifted and shifted signals is the Smartshift's biggest problem, though as I pointed out earlier, whether or not it's a problem depends on what sounds you want to put through the unit. But there's no denying the almost unique sophistication of the IPS33's harmonisation abilities, nor the cleanness of its pitch-shifted signal outputs. If you want to make sweet harmony, your smartest move might just be to invest in an IPS33.

Price £825 including VAT

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DAT's Life

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HB Engraver

Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.


Music Technology - Jul 1989

Gear in this article:

Studio FX > Digitech > IPS33

Gear Tags:

Digital FX
Pitch Shifter

Review by Simon Trask

Previous article in this issue:

> DAT's Life

Next article in this issue:

> HB Engraver

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