Antares ATR1

Paul White tries out something that he wishes had been available back in his intensive gigging days — a box that automatically puts your vocals in tune in real time!

Back in the August 1997 issue of SOS, I reviewed an impressive piece of software by Antares called Autotune designed to correct imperfectly pitched vocals. At the time it was only available for Pro Tools TDM systems, but has since been made available both as a Cubase VST plug‑in and as a stand‑alone product. The program I reviewed had two basic modes of operation: an automatic mode that corrected a monophonic vocal line to the nearest notes in a user‑definable scale, and a graphical mode that allowed surgically precise corrections to be made to individual syllables via a graphical interface. The device reviewed here is a single‑channel hardware box running a real‑time version of Antares' automatic pitch‑correction algorithm.

The ATR1 works by tracking the pitch of a monophonic voice or instrument up to a maximum pitch of C6 and then comparing the measured pitch with an input MIDI note (either from a keyboard or sequencer), a preset scale or a scale set up by the user. If the signal is correctly pitched, no change is made, but if the pitching is out, a clever pitch‑change algorithm increases or decreases the pitch to match the selected MIDI note or the nearest note in the currently selected scale. Because the pitch of the original signal has to be read before the pitch‑shifting can operate, there is a slight processing delay depending on the pitch of the original sound, but this is claimed to be less than 4 milliseconds, which in the context of a vocal line isn't long enough to be noticeable.

Because the ATR1 relies on pitch tracking, it can't work on complex mixes or ensemble voices, and even a solo voice can resist tracking if it includes very breathy, non‑pitched sounds. Though there's little that can be done about ensemble sounds, the ATR1 does include a Sensitivity control that makes it a little more forgiving when difficult‑to‑track breathy sounds are being processed.

A real vocal performance is never precisely in tune but instead fluctuates a little to either side of the pitch centre. To remove all these fluctuations would make the voice sound unnatural, so the ATR1 provides control over how rapidly off‑key notes are brought to the correct pitch. Some musical instruments benefit from fast correction whereas a voice that includes natural glides and vibrato needs to have a slower processing response time. In addition to being able to correct pitch in this way, the ATR1 can also add vibrato to a voice with similar parameters to the modulation you find on a synth — depth, rate and onset delay.

Hardware

Physically, the ATR1 is a 1U rackmount device powered from an included external mains supply adaptor. It has balanced XLR inputs and outputs as well as a balanced jack input and an unbalanced jack output. A further jack socket accepts a footswitch that can be set to operate as a Bypass or to step through Programs and Songs, but given that this unit is also intended to be suitable for live use, it seems somewhat penny‑pinching not to have supplied two footswitch jacks so you could do both. To help minimise ground loop problems, there's a switch to choose between circuit ground and chassis ground — you simply try both and use the quietest. There's also a MIDI In socket for remote program selection, but no MIDI Out for SysEx dumps. However, pretty much all the internal parameters can be accessed using SysEx, so there's no reason somebody couldn't write an editor for this machine.

The front panel is simple, clearly labelled and smartly businesslike, though there's no power switch. Dominating the left‑hand side of the panel is the 20‑character, two‑line backlit LCD display with an adjustable viewing angle accessed via the System setup page. Data entry is via a large knob connected to a shaft encoder, and a pair of buttons move the cursor in the display window. Program accesses the edit pages for Program and Song editing modes while the Page button cycles through the available edit pages. You can't reverse the direction of cycle, which is mildly irritating, but there are relatively few pages to go through, so it's not too much of a problem. Other than that, there's the System button for setting global parameters, such as MIDI, LCD angle and so on, and a Bypass button to switch the processor out of circuit. This works silently so it could be used live.

Finally, there are two LED meters — one to show the input level and one to show how much pitch change is being applied up to a maximum of plus or minus 90 cents.

Modes

The ATR1 operates in one of two modes, Program mode or Song mode. In Program mode, you can use any one of 50 Programs, each of which comprises a musical scale, a Speed setting and any vibrato settings you may wish to apply. If a song uses the same musical scale all the way through, this is probably the most convenient mode to use, though if there is a key change, you can step between two or more programs using the footswitch or via MIDI Program Change commands. One of the factory Programs is chromatic, so providing the singer never drifts by more than half a semitone, you can use this for everything. However, you'd be surprised just how many singers do wander outside these limits on occasions, so specifying a scale is safer! The user can set up any scale required, but there's also a useful facility for bypassing certain notes within the scale so they aren't processed. For example, if a singer only has problems pitching Cs and Ds, all the others could safely be bypassed so as to reduce unnecessary processing.

As a stand‑alone solution to vocal (and some monophonic instrument) intonation problems, the ATR1 is unique...

The other option is Song mode, which comprises 20 Songs, each of which can hold up to 15 steps. Each step can contain one Program with its associated scale or one of several so‑called Navigation controls that allow the user to insert loops of Program groups or to include steps where no processing is required. This would probably only be used for live performance as, in the studio, you can stop recording and switch to a different program. During performance, you can move through the steps using the footswitch or via MIDI. When in Song mode, the Song's vibrato and tracking Speed settings over‑ride those in the individual Programs, so the Programs are really only defining the musical scale valid for that section of the song to which they relate.

Pitch and vibrato may be controlled via MIDI, either directly from the keyboard or sequencer as explained earlier, or by using the bend and mod wheels on a keyboard up to a maximum of +/‑ one tone bend range and up to the maximum vibrato depth set in the Program. It's also possible to assign a MIDI controller to vary the Speed setting by overriding the value set in the current Song or Program. When the program or Song is changed, the stored Speed value is again used.

Using The ATR1

To use the ATR1, you can either use one of the musical scales provided, create your own by the simple expedient of turning on or off each of the notes in the chromatic scale until you get what you want (notes that you don't want processed can be bypassed individually by placing an asterisk beneath the note name), or you can input the correct pitches in real time via MIDI.

Once you've chosen a scale to suit the piece of music being worked on, all you need to do is feed audio through the box, though if the master tape isn't in concert pitch, you can offset the tuning of the ATR1 first. It is possible to use the ATR1 live or while recording, but it's important to prevent the singer hearing the corrected sound or their pitching is likely to go all over the place as they attempt to compensate. For stage use, the uncorrected vocal should be fed through the stage monitors.

For singers who are reasonably precise and don't use excessive vibrato, chromatic scale works pretty well. The trick is in setting up the Speed parameter to get a natural result. Set it too fast and the voice almost yodels to the correct pitch, especially if it was a long way out to start with, but if you set Speed too slow, the note still won't be fully corrected by the time a new pitch is sung. If the singer tends to use a lot of vibrato or to scoop notes, then the chromatic scale is likely to throw up unwanted semitone trills and slurs, and if the pitching is poor, the closest note might actually end up being a semitone out from the correct one — which is a dead giveaway. In such cases, using the appropriate scale invariably gives better results as there are no 'illegal' notes to jump to. Providing the original performance is reasonably competent, it's usually possible to bring about a great improvement without the voice sounding processed. Really hopeless cases require more work to hide the side effects!

In addition to correcting intonation errors, the manual makes several creative suggestions, including a way to fake double tracking by mixing the corrected and uncorrected vocals. The ATR1's detuning and vibrato can be used to emphasise the effect if needed. Furthermore, by selecting a scale with only a few notes in it, then by using a fast Speed setting, you can simulate some ethnic vocal styles or impossible octave leaps and trills.

Summary

As a stand‑alone solution to vocal (and some monophonic instrument) intonation problems, the ATR1 is unique, though it isn't as flexible as the non‑real time, graphical editing capabilities of its software‑based counterpart. For example, using the Autotune software, a single drooping note can be edited by dragging curves on a screen to achieve a very natural result. The automatic mode of the Autotune software is comparable with the way the ATR1 works, and the fact that it's so easy to operate means that you are likely to use it far more often than off‑line graphical editing. Singers with apparently good pitching can usually be tightened up a little further with this unit, and even fairly indifferent performers can be made to sound much more precise. Providing the pitch correction required is in the order of tens of cents rather than whole semitones, there are few if any discernable processing artifacts, and user parameter adjustment is largely limited to varying the Speed for the most natural result. Of course there are vocalists who even the ATR1 can't help, but perhaps their money would be better spent on singing lessons!