MPC vocal effects: the smallest category, all three of them

The short version

This site's own insert vs send/return effects article counted every category in the shared 98-effect catalog, and Vocal came in dead last by a wide margin:

"Delay/Reverb 23, Dynamics 14, EQ/Filter 17, Harmonic 19, Modulation 22, Vocal 3, total 98."

Three effects, and they don't split evenly into "adds voices" versus "corrects pitch." AIR Vocal Doubler adds up to eight offset copies of a lead voice with no music-theory awareness at all, no Key or Scale field anywhere in its table. AIR Vocal Harmonizer adds up to four scale-aware harmony parts, built around a Key/Scale pair. AIR Vocal Tuner adds nothing, it corrects the one voice already there, but shares that same Key/Scale pair with Harmonizer, plus an identical 420.0–460.0 Hz Reference pitch field. Doubler and Harmonizer, meanwhile, both have a field called Lead Volume and a field called Timing, and neither field means the same thing on both effects.

Where these live: the Vocal category

Same shared 98-effect list this site has already mapped across five prior articles, one insert-or-send/return catalog split into six categories. Vocal's own "Options:" line is the shortest of the six by a wide margin:

"Options: AIR Vocal Doubler, AIR Vocal Harmonizer, AIR Vocal Tuner"

The whole category fits on two printed pages, PDF pp.420–421, right after Modulation's own six-page run ends. With this article, five of the catalog's six categories now carry dedicated coverage on this site: Dynamics, EQ/Filter, Delay/Reverb, and Modulation already shipped, Vocal closes here, and only Harmonic, the catalog's second-largest category at 19 entries (AIR Amp Sim, AIR Distortion, Decimator, Granulator, TouchFX, XYFX among them), remains open.

AIR Vocal Doubler

Akai's own description is short and doesn't mention pitch correction, key, or scale anywhere:

"This effect creates realistic vocal doubles to add width or thickness to a vocal line."

Parameter	Range	Default
Voices	1–8	4
Stereo Spread	0–100%	70%
Lead Volume	−Inf – +6.0 dB	0.0 dB
Doubler Volume	−Inf – +6.0 dB	0.0 dB
Pitch	±0 – 250%	±38%
Pitch Speed	0–100%	75%
Timing	0–800 ms	63 ms

Seven fields, none of them Key, Scale, or Reference pitch. Pitch itself is a plus/minus percent (±0–250%), not cents or semitones, Akai's own table gives no conversion between the two units and this article isn't guessing one. Voices sets how many offset copies play at once, up to eight, and Stereo Spread sets how wide those copies sit in the field; Lead Volume and Doubler Volume are two separate trims, one for the original signal and one for the added copies, both sharing the same −Inf to +6.0 dB range and 0.0 dB default.

AIR Vocal Harmonizer

Harmonizer's own description names the feature Doubler's doesn't have, music theory:

"This effect can create up to four-part realistic vocal harmonies and complex doubling effects. Each vocal part has its own level, delay, formant, mode, and interval parameters."

Parameter	Range	Default
Key	A–G#	C
Scale	Major, Minor, Harm Minor, Melo Minor, Dorian, Phrygian, Lydian, Mixo, Locrian, Chromatic, Penta, Maj Triad, Min Triad, Root	Major
Lead Volume	−Inf – 0.0 dB	0.0 dB
Harmony Volume	−Inf – 0.0 dB	−2.5 dB
Timing	0–100%	42%
Tuning	0–100%	14%
Smooth	5–200 ms	8 ms
Voice Range	Very Low, Low, Mid, Mid High, Very High	Mid
Root Mode Split	A–G#	E
Reference	420.0–460.0 Hz	440.0 Hz
Delay Sync	Off, On	On
Harmony 1–4	Off, On	printed as "1 On" (see note below)

Twelve fields, the densest table in this category by a wide margin. The Harmony 1–4 row's own default reads "1 On" in the extracted table, which this article is reading as only the first harmony part defaulting on and parts 2 through 4 defaulting off, consistent with a four-part harmonizer not stacking all four voices before you've chosen to, but the manual's own table doesn't spell that reading out in a full sentence, so it's disclosed here rather than stated as certain. Lead Volume tops out at 0.0 dB, not the +6.0 dB Doubler's own Lead Volume field allows, and Harmony Volume defaults to −2.5 dB rather than Doubler's 0.0 dB default on the equivalent second-voice trim.

AIR Vocal Tuner

Tuner's description is the only one of the three that names pitch correction directly:

"This effect applies pitch correction for natural sounding or hard-tuned vocal effects."

Parameter	Range	Default
Detection	Unworried, Default, Selective, Picky, Blind	Default
Voice Range	Very Low, Low, Mid, Mid High, Very High	Mid
Key	A–G#	A
Scale	Major, Minor, Harm Minor, Melo Minor, Dorian, Phrygian, Lydian, Mixo, Locrian, Chromatic, Penta, Maj Triad, Min Triad, Root	Minor
Retune Time	1–1000 ms	32 ms
Reference	420.0–460.0 Hz	440.0 Hz

Six fields, the shortest table of the three. Detection is the one field with no equivalent anywhere else in this category, five named tracking modes running from "Unworried" (loosest) to "Blind" (presumably the most aggressive, though Akai's own table gives no further description of what separates the five beyond the names themselves), controlling how the pitch-detection algorithm reads the incoming signal before Retune Time decides how fast it corrects toward the target note.

Shared fields, different rules

Diffed field by field across all three tables above, not assumed from the shared naming:

Field name	On Doubler	On Harmonizer	On Tuner
Lead Volume	−Inf – +6.0 dB	−Inf – 0.0 dB	no equivalent field
Timing	0–800 ms	0–100%	no equivalent field
Key / Scale	no equivalent field	A–G# / 13-scale list	A–G# / 13-scale list, identical option set
Voice Range	no equivalent field	5-step Very Low–Very High	5-step Very Low–Very High, identical option set
Reference	no equivalent field	420.0–460.0 Hz / 440.0 Hz	420.0–460.0 Hz / 440.0 Hz, identical range and default

Two real traps sit in that first pair of rows. Lead Volume exists on both Doubler and Harmonizer with the exact same name, but Doubler's copy can push the original signal up to +6.0 dB while Harmonizer's copy caps at 0.0 dB, unity gain, no boost available at all. And Timing exists on both with the exact same name, but it isn't the same kind of field, Doubler's Timing is a straight millisecond delay (0–800 ms) while Harmonizer's Timing is a percent (0–100%) with no stated millisecond equivalent anywhere in the table, reading a "63" carried over from Doubler onto Harmonizer's Timing knob would set something close to two-thirds of whatever range Harmonizer's own percent scale covers, not 63 milliseconds of anything.

Harmonizer and Tuner, by contrast, genuinely share structure: identical Key range (A–G#), the exact same thirteen-entry Scale list word for word, the same five-step Voice Range list, and byte-identical Reference field (420.0–460.0 Hz, default 440.0 Hz). What differs between the two is only the defaults, Harmonizer opens on Key C / Scale Major, Tuner opens on Key A / Scale Minor, Voice Range defaults to Mid on both. Doubler has none of these five fields, full stop, it doesn't track key or scale at all.

Side by side

Effect	Fields	Key/Scale aware	Adds voices	Corrects pitch
AIR Vocal Doubler	7	No	Yes, up to 8	No
AIR Vocal Harmonizer	12	Yes	Yes, up to 4	No, tunes to the chosen interval, not a fixed reference pitch of the source note
AIR Vocal Tuner	6	Yes	No	Yes

Common mistakes

Mistake: assuming Lead Volume behaves the same on Doubler and Harmonizer because the field name matches. Doubler's Lead Volume can boost the original signal up to +6.0 dB; Harmonizer's Lead Volume caps at 0.0 dB with no boost headroom at all.

Mistake: carrying a Timing value over from Doubler to Harmonizer, or the reverse. Doubler's Timing is milliseconds (0–800 ms); Harmonizer's Timing is a percent (0–100%) with no stated ms equivalent. The two knobs don't measure the same thing despite the identical field name.

Mistake: expecting AIR Vocal Doubler to track a key or scale. It has no Key, Scale, or Reference field anywhere in its seven-field table; the Pitch field is a plain plus/minus percent detune, not a musical interval. Key/Scale awareness is a Harmonizer and Tuner feature only.

A note on manual versions

Every parameter table above is checked directly against Akai's Standalone OS User Guide, Manual Version 3.9, cross-checked line-for-line against Manual Version 3.7. A direct diff of both manuals' Vocal-category pages (v3.9 PDF pp.420–421, v3.7 PDF pp.399–400), normalized for whitespace and page-number lines, returned zero content differences, every effect name, description sentence, and parameter value identical between editions. The chapter sits at the same flat plus-21 page offset between versions this site keeps finding across the manual (420 minus 399 equals 21, 421 minus 400 equals 21), a sixth confirmed data point that the whole effects appendix shifted as one contiguous block between v3.7 and v3.9 rather than section by section.

Verdict

Run into a session where Harmonizer's percent-based Timing field tripped you up expecting Doubler's milliseconds? Tell us about it.