Plural of harmonizer; multiple people or devices that create harmony or bring things into agreement.
Harmonizer + -s plural marker. This is the straightforward plural of the agent noun harmonizer.
In music production, harmonizers are sometimes used in recording, but many musicians consider them 'cheating' because they don't require the skill of finding harmony by ear. But they're also accessible tools that let people with limited music training create professional-sounding arrangements.
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