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Digitech Smartshift

Smarter than the average pitch shifter?

David Mellor assesses the musical intelligence of the DigiTech IPS33 SmartShift intelligent pitch shifter.



When I was but a lad, I was instructed in the ways of musical harmony. How to write a chorale in the style of Bach, and how to imitate the counterpoint of the 17th century masters. But I never was much good at it, and it took me years to unlearn all the strict rules I had been taught and produce a piece of real musical (and financial) worth.

What I did learn to appreciate is that music is like a language with many dialects. And a good composer, like a good linguist, can benefit from the study of different cultures and modes of expression. Drawing only on your own resources will ultimately drain the well dry. Incorporating outside influences into your music will enrich its variety and range.

At the basis of music are systems of scales - series of notes which make up a musical octave. There are many ways of dividing up the frequencies of sound vibrations into these scales: diatonic, chromatic, pentatonic, whole tone, to name a few. Eastern music has its various scales, too. Indian music, for example, uses different scales - or 'ragas' - as a basis for musical improvisations for different occasions and different times of day.

Most Western music is based on just two scales: Major and Minor. If you go to your keyboard and play an ascending series of eight white notes starting on C, you will play a Major scale. Do the same starting on A and it will be a Minor scale. The distinguishing feature of these scales is the pattern of tone and semitone intervals. The Major scale goes like this: tone-tone-semitone-tone-tone-tone-semitone C-D-E-F-G-A-B-C

The Minor scale is as follows: tone-semitone-tone-tone-semitone-tone-tone C-D-Eb-F-G-Ab-B-C

These patterns can be transposed (moved up or down in pitch) to start on any note. A Major scale in the key of D follows the Major pattern, but now black notes have to be incorporated to keep the pattern correct.

Other scales - called Modal scales - can be obtained in the same way. A series of white notes starting on D will produce the Dorian mode. Starting on F produces the Lydian mode, and these modes can be transposed in the same manner as Major and Minor scales (which, strictly speaking, are modes too).

To get a flavour for the characteristic sounds of these modes, find a piece of music that you can play purely in the key of C, ie. without any black notes. If you shift your hands up a tone from C to D, you can play the same piece in the Dorian mode and it will take on a distinctly different flavour. Dorian, by the way, is particularly good for sea-shanty type pieces.

It should be obvious that there are seven of these modes, one for each of the white notes; and by restricting ourselves to just two, Major and Minor, we are actually rejecting five perfectly good creative alternatives.

Another quite different scale is the Whole Tone scale, which goes like this: tone-tone-tone-tone-tone-tone C-D-E-F#-G#-A#-C There are just seven notes in a complete octave this time, but try improvising using just these notes, over the whole keyboard perhaps, and see what wonderful atmospheric ideas appear almost of their own accord.

INTELLIGENT HARMONISATION



Somewhere, I imagine, in the DigiTech research headquarters works a highly trained musician, surrounded by rows of keyboards and shelves of textbooks on the theory of musical scales. And recently he has been working hard, with electronic engineers and software designers, to produce the DigiTech IPS33 SmartShift intelligent pitch shifter. And what they have come up with is perhaps as much a musical research tool as studio effects unit.

There are currently several pitch shifting units on the market. Those that are dedicated to the pitch changing effect, and others which incorporate it within a range of multi-effects. It is rapidly becoming possible to produce real-time pitch shifting to a quality similar to that of speeding up a tape, or replaying a digital sample at a higher pitch. The pitch shifter, of course, performs the transposition without stretching or compressing the sound in time.

Such processing has its limits. Most pitch shifters introduce a warbling effect into the sound they are processing. Sometimes this is not unpleasant, but often it is. The warbling tends to increase at greater degrees of pitch shift, or when the sound being processed is polyphonic. Obviously, pitch shifting an orchestra playing perhaps a dozen different notes simultaneously, together with miscellaneous percussion, is never going to be a trivial task.

The DigiTech SmartShift circumvents the polyphony problem in a very simple way - its software is dedicated to single note processing. Play two notes at a time and a distinctly odd harmonisation is the result. (Quoting from the manual: 'Chords can create interesting, and usually unmusical effects.') But because the IPS33 is able to concentrate completely on the task of shifting single notes, it is able to do that particularly well. So well, in fact, that the pitch shifted output can be used on its own - not merely as a 'thickener' to the unshifted, original sound. For instance, it is possible to reliably produce a very usable bass guitar sound from a normal six-string guitar. I wouldn't bank on being able to do that with other pitch changing units. (As well as large interval pitch shifting, there is also a Detune mode which can accept a polyphonic input, but only pitch shift it by a small amount).

The main aim of the DigiTech SmartShift is to produce harmony from a single note input. The input is mono, and from this two pitch shifted outputs are created. The SmartShift is able to analyse the pitch of the incoming note, and from it produce harmony notes from any selected (or user-created) key and scale. The harmony notes are (except in the case of Chromatic harmony) pitch-quantised, ie. they are always bang on pitch - even if the input wavers about slightly. With vocals, this can produce some interesting effects, which I'll examine later.

KEYS AND SCALES



The DigiTech SmartShift is provided with 83 preset pitch shift programs covering a large range of the theoretical musical possibilities. But seeing as the possibilities, as I indicated above, are practically limitless, there are also 15 user presets, and a bypass setting. Any of the factory presets can be overwritten if desired, but they are always safe and retrievable from ROM, if necessary. In addition to the presets, there are 16 user-defined harmony memories, where harmonies other than those offered by the manufacturer can be set up. Each factory preset contains information covering scale type, key, and transposition intervals. Let's examine these...

The scale setting determines which notes may appear at the pitch shifted outputs. For example, if you were harmonising in the key of C Major, you would want only notes from that scale to be selected. Therefore, whatever the note of the input, it must be pitch shifted to a note chosen from C, D, E, F, G, A, B - or C, an octave higher or lower. This is called the Major Diatonic scale ('diatonic' simply means using only the notes from the key). In all, there are 15 scale types: Chromatic, Major, Minor, Harmonic Minor, Melodic Minor, Dorian, Mixolydian, Lydian, Lydian Augmented, Whole tone, Half-whole, Whole-half, Major Pentatonic, Minor Pentatonic, Blues.

Also, there are as many as five variations of each type, giving you a choice of 59 different scales (plus detune scales and user-definable harmonies). I'll leave it to the potential purchaser to discover how exotic some of these are!

In their raw state, these scales are all in the key of C - the beloved 'easy' key for keyboard players. Of course, guitarists would have preferred A, and saxophonists Eb or Bb (for alto and tenor sax respectively), but each of the scales can be transposed to any of the 12 possible keys very easily.

So far, we have covered the notes which may be chosen. We need to set the two harmony notes that actually will be chosen. These are known as the Transposition intervals. A simple example would use the C Major scale and have the transposition set to produce the notes E and G from a note input of C - the basic Major triad (chord) consisting of the intervals of a third and a fifth. Now, when any of the other notes in the C scale are input, the harmonies will stick to the third and fifth interval pattern, but swap between Major thirds (an interval of four semitones) and Minor thirds (three semitones) where necessary to keep within the key. Inputting the note E gives harmony notes of G and B. A conventional pitch shifter, which doesn't understand the rules of harmony, would have produced a G#, which is definitely not in the key of C Major.

USER-DEFINED HARMONY



User-Defined Harmony, or UDH (not to be confused with the Union of Democratic Hairdressers) is a method of producing user scales for the SmartShift to operate on. This actually goes one step beyond the system of scales and transpositions outlined above.

Creating a UDH involves defining a pair of notes, for each note you may input, which will be the harmonies for that particular note. Setting a scale and transpositions is not true harmony, just a way of making sure that the pitch shifted notes will have a degree of relevance to the key you are playing in. UDH ensures that every note of a melody line will be harmonised with exactly the notes you want. Let's try an example.

Suppose you have a tune in the key of C Major. According to the conventional rules of harmony, it could be accompanied like this:

Melody note Harmony 1 Harmony 2
C E G
D G B
E G C
F A C
G B D
A C F
B D G
C E G

This is harmony according to the good old 'three chord trick', where chords of C, F and G can harmonise any of the notes of the scale of C Major:

Note Possible chord
C C or F
D G
E C
F F
G C or G
A F
B G
C C or F

This would produce a very straightlaced harmony, but you can be as adventurous as you like wiith the SmartShift. Any melody note can be harmonised by any pair of notes, including sharps and flats, within a two octave transposition range.

HIGH STANDARD OF PERFORMANCE



Because it limits itself to the harmonisation of single note input, the DigiTech SmartShift is capable of a very high standard of performance. The glitching and warbling normally experienced with other pitch shifters is almost completely absent. And as far as pitch recognition goes, given a good strong signal, the SmartShift will hardly put a foot wrong. It does take a little time to work all this out, and the pitch shifted outputs are, I estimate, 30 to 40 milliseconds behind the input. But there is no way even the most intelligent pitch shifter can get around this, unless it can see into the future.

As I touched on earlier, the Chromatic pitch shift scales on offer always transpose by the same harmonic interval and do not use pitch quantisation, so any out-of-tuneness of the input is reflected in the harmony outputs. However, other scales do pitch quantise, resulting in harmonies that are always in tune with concert pitch (A=440Hz), even if the input signal is slightly off. The emphasis here is on slightly, because if the input pitch wavers by more than a quarter of a tone, SmartShift will interpret this as a new note on the adjacent semitone. This results in a wrong harmony. I'm afraid that the only way to look at this is from the 'garbage in - garbage out' philosophy. Or, you can't make a silk purse out of a pig's grunt!

My vocalisations are a little more musical than porcine ululation (but only slightly), and I found myself unable to sing sufficiently in tune to stimulate reliably the creation of the correct harmonies. Trained singers, with restrained vibrato, ought to manage better. One might be persuaded to take a different view of this, that with a little practice vocal pitching may become more precise, resulting in correct harmony and a better singing technique.

Guitar playing fared better - a lot better. Take your axe down to your local DigiTech dealer and have fun producing the type of harmonies it takes the playing skill of a Brian May, and lashings of overdubs, to achieve normally. I fully intend incorporating as many superflash harmony guitar solos into my recordings as I am able, before my review sample SmartShift is recalled to its maker.

MUSICAL DEVELOPMENT



As well as being an immensely useful addition to any studio effects rack, the DigiTech SmartShift will also provide a creativity injection to music that has so far been based on the conventional Major and Minor scales.

I found it very instructive simply to improvise on a synthesizer into the unit and experiment with the many different scales available. What will this tune sound like harmonised with notes from the Mixolydian diminished scale? It's very easy to try it out with the SmartShift, and even if you don't use the sounds it produces in an actual recording, the same harmonies could be duplicated by another voice or instrument.

Even if you already have a pitch shifter in your studio rack, there ought to be a space for a DigiTech SmartShift. The sound quality of the effects is very good, and the range of musical scales and harmonies it can produce must surely be a strong incentive towards increased creativity.

FURTHER INFORMATION

£825 inc VAT.

John Hornby Skewes & Co Ltd, (Contact Details).

TUNING

For intelligent harmonisation, the input signal to the SmartShift must be in tune with concert pitch (A=440Hz). SmartShift itself cannot be tuned, therefore the input must be. As an aid, DigiTech provide a Tune function which uses the 7-segment LED displays to show whether a note is sharp, flat, or perfectly in tune.


DETUNE

As well as the musical scales described in the main text, there are four Detune scales which can be used to obtain a chorus effect, but without the hindrance of cyclic variation that occurs with standard delay line chorusing techniques.

Detune 1 can provide two slightly pitch shifted outputs for polyphonic and monophonic sources. Detune 2, 3 and 4 provide progressively more detuning, up to approximately a quarter tone.


SMART PHYSIQUE

The DigiTech IPS33 SmartShift is a 1U rack mounting unit. The front panel has LED mode indicators for:

- Preset Select
- Scale Number
- Harmony Define
- Tuning
- Key
- Note
- Preset Save
- Transpose 1
- Interval 1
- Bypass
- Transpose 2
- Interval 2

Two function select buttons are used to access these modes. Parameters are altered by Up and Down nudge buttons. The display is four 7-segment red LEDs.

Rotary controls are provided for Output Level, Output Mix and Input Level, and there is a four-stage LED headroom meter.

The rear panel has one input (¼" jack, balanced or unbalanced) and two outputs: Harmony 1/Mono, Harmony 2. The input level is switchable between high and low sensitivity. Unfortunately, the panel labelling does not make clear which switch position is which.

A send and return insert point is available, which DigiTech suggest you use to connect to a distortion unit. A bypass footswitch socket is also available.

Finally, MIDI sockets (In, Out, Thru) are provided for Program Change and System Exclusive program storage.


Also featuring gear in this article



Previous Article in this issue

A Case for Quality Microphones


Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

 

Sound On Sound - May 1989

Donated & scanned by: Mike Gorman

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Review by David Mellor

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