UnderTone Audio UnFairchild 1.0.8 (macOS)

Getting a hardware vari-mu compressor sound in a plugin that actually behaves like the real thing is rare. The UnderTone Audio UnFairchild is a software recreation of the UnFairchild 670M mkII, built with MIXLAND and Eric Valentine. It works as a standard plugin in most DAWs on macOS and Windows.

• Supports macOS 10.13 and later, both Intel and Apple Silicon (ARM).
• Includes side chain processing for frequency-conscious compression.
• MS function for mid/side processing on stereo tracks.
• Wet/dry control for parallel compression without extra routing.
• Output level control and true bypass for clean A/B comparisons.
• Suitable for drum bus, mix bus, or individual tracks needing character.

Drop it on the drum bus before EQ

The UnFairchild works best on sources where a hardware vari-mu would normally go. I tend to drop it on the drum bus or a vocal group before any EQ. The wet/dry control means I can dial in parallel compression inside the plugin rather than building a return track. The MS function is useful on stereo room mics or a mix bus where you want to treat centre and sides differently. Side chain processing lets me duck the compression on kick hits or sibilance without an external trigger.

It plays well with other plugins in the chain. Put it before a transient shaper if you want to soften attacks first. Put it after an EQ if you want compression to respond to a specific frequency range. The true bypass makes A/B switching honest — no level jumps to fool your ears.

MS and side chain options surpass the CLA-76

Three other vari-mu style plugins come to mind when I reach for the UnFairchild. The Waves CLA-76 is faster and punchier but lacks the MS and side chain options the UnFairchild has. It is better for individual tracks that need aggressive limiting, not for a whole bus that needs gentle glue.

The iZotope Ozone Dynamics module is more surgical. It has multiband control and a spectral shaping mode, but it does not sound like a valve compressor. The UnFairchild gives you the colour and the THD control; Ozone Dynamics gives you precision without character.

The Kazrog Kclip is not a compressor at all — it is a clipper with a soft knee mode — but people reach for it on drum buses for similar reasons. The UnFairchild is a better fit if what you want is compression that breathes, not clipping that chops peaks.

None of these three offer the DC Threshold or Feed-Back/Feed-Forward switching the UnFairchild has. If your workflow relies on those controls, the UnFairchild is the only one in this group that gives them.

Rock and indie mix engineers using vari-mu character

Mix engineers working on rock, indie or pop benefit most. The vari-mu character suits drum bus and vocal processing where you want the compressor to pump naturally rather than clamp down. Mastering engineers will use the MS function and the wet/dry control to add subtle glue without over-compressing. Post-production users who need a clean, true bypass and side chain for dialogue or Foley will find it useful, though the English-only interface may be a limitation for non-English speakers.

If you work in a genre that needs aggressive, fast compression — metal, electronic, hip-hop — the UnFairchild is probably not your first choice. You would look at an FET or digital compressor first. But if you want a software version of a hardware vari-mu that includes THD, parallel processing and MS, this is the one.

The interface is English only. The plugin runs as VST, AU, or AAX depending on your host. Installation and activation instructions come in the package.

• macOS 10.13 or later
• 64-bit Intel or Apple Silicon processor
• Windows 7 or later (64-bit)
• Supported plugin formats: VST2, VST3, AU, AAX