AfterMix.io — AI Track Mastering in Your Browser

AfterMix.io is a free, browser-based audio mastering tool built for AI-generated music. Upload a raw track from Suno, Udio, or any other AI music generator, and AfterMix.io polishes it to a professional master in seconds — no plugins, no DAW, no account required. Everything runs locally in your browser via the Web Audio API; your audio never leaves your device.

The Problem with AI-Generated Music

AI music generators produce tracks with a characteristic "AI sheen": brittle high frequencies, metallic "birdie" artifacts in the 2–10.5 kHz range, inconsistent loudness, and a lack of the analog warmth and glue that professional mixes have. AfterMix.io addresses all of these issues with a focused mastering chain designed specifically for AI audio.

How It Works

Drop an audio file onto the page (MP3, WAV, AAC, FLAC, or any format your browser supports). AfterMix.io analyses the track — measuring integrated loudness in LUFS, true peak level in dBFS, and a proprietary Harshness score — then runs the track through a multi-stage master chain. When processing is complete you can A/B compare original and processed audio, tweak any parameter, and download the result as a WAV file.

Easy Mode

Three macro sliders cover the most common adjustments:

  • Smooth — controls the overall de-harshness amount. Higher values apply more aggressive spectral repair and dynamic limiting in the harsh frequency band.
  • Warmth — boosts the low-mid body around 200 Hz and adds tape-style harmonic saturation for a fuller, rounder sound.
  • Loudness — targets a specific integrated loudness (LUFS) and applies a true-peak limiter to hit streaming platform standards.

One-click presets in Easy mode include: Streaming (−14 LUFS, clean), Warm Vinyl (saturated, wide), Podcast (speech-optimised loudness), and Punchy (heavy glue compression).

Pro Mode

Pro mode exposes six independent processing tabs for fine-grained control:

De-harsh

  • Amount — overall de-harshness level (0–100%)
  • Adaptive Scaling — scales the de-harsh intensity relative to the auto-detected excess energy in the harsh band
  • Dynamic De-harsh — spectral repair mode that clamps harsh bursts (2–10.5 kHz) only when they spike above a dynamic threshold, removing metallic birdie artifacts without dulling steady high-frequency content

Character

  • Tape Saturation — applies soft even-order harmonic saturation across the full spectrum for analog density and mix glue
  • Harmonic Exciter — synthesises natural air above 7.5 kHz from lower harmonics, replacing the brittle AI sizzle with organic high-frequency content

Tone (3-Band EQ)

  • Warmth (200 Hz) — ±6 dB shelf for low-mid body
  • Air (12 kHz) — ±6 dB high shelf for presence and openness
  • Highpass — variable high-pass filter (20–120 Hz) to remove sub-rumble

Glue Compressor

  • Threshold — compression onset level (−60 to 0 dBFS)
  • Ratio — compression amount (1:1 to 20:1)
  • Makeup Gain — post-compression output gain (0–12 dB)

Stereo

  • Stereo Width — Mid/Side width control (0% = mono, 100% = original, 200% = maximum widening)

Loudness

  • Target LUFS — integrated loudness target (−24 to −6 LUFS); −14 LUFS for Spotify/Apple Music streaming
  • True Peak Ceiling — maximum intersample peak (−3 to 0 dBFS); −1 dBTP is the streaming standard

Technical Details

AfterMix.io is built with React, TypeScript, and the Web Audio API. All DSP runs on the client: spectral analysis uses an FFT of 2048 bins; the harshness score is derived from the integrated energy in the 2–10.5 kHz band relative to the full-band RMS; loudness measurement follows the ITU-R BS.1770-4 standard. No audio data is transmitted to any server.

Who Is AfterMix.io For?

AfterMix.io is for musicians, content creators, game developers, and hobbyists who use AI music generators (Suno, Udio, Bing Create, MusicLM, or similar) and want a fast way to make their AI tracks sound less artificial and more polished before using them in videos, games, podcasts, or social media content.

Made with love by Bragi Helvig.