SUS4 Mix Check

SUS4 Mix Check measures your mix and sets it against a reference track or a streaming loudness target, so you catch level mistakes before they reach the master. Available on iPhone, iPad and Mac, it reads integrated, short-term and momentary loudness, loudness range, true peak, stereo correlation and a five-band tonal balance, and shows your mix and the reference side by side.

Choose a target such as Spotify, Apple Music, YouTube or EBU R128 broadcast and the app grades your mix against it, with a plain-English verdict and a list of likely problems. Load a reference and you get a written comparison: how much louder or quieter, brighter or darker, wider or narrower your mix is. You can analyse a whole file, just a section of one, or live input from the microphone or an interface.

Reference comparison is standard practice in professional mixing for a reason: your ears adapt to the room and the mix after long sessions, and objective numbers break that adaptation. SUS4 Mix Check keeps a history of every take, so you can pin two versions and compare them A/B on the same loudness graph and spectrum.