Your phone is the tuner you always have with you. It's also, out of the box, a device engineered to make your voice sound good on calls — which is nearly the opposite of what accurate pitch measurement wants. Phone audio pipelines suppress noise, squash volume swings, and quietly filter out low frequencies. Great for your mum hearing you clearly. Not great for tuning a bass.
None of this makes phone pitch detection bad. It makes it something you set up with two minutes of care. Here's what's going on and what to do about it.
Tuner apps on the store want a download, then permissions, then increasingly a subscription for the "pro" accuracy tier. A browser-based detector runs the same math — the Web Audio API gives a web page the same raw samples an app gets — with nothing to install and nothing to pay. The core algorithm, autocorrelation, has no pro tier. It's the same math from a 1960s signal processing textbook whether you paid $4.99 or not.
One genuine advantage apps used to have was offline use. A PWA closes that gap: this detector installs to your home screen from the browser and runs with no connection at all.
Three things, mostly.
Noise suppression decides what counts as "noise" and removes it. A long steady tone — exactly what you produce while tuning — looks a lot like background hum to that algorithm. Some phones will fade your sustained note out mid-reading.
Auto gain control rides the volume up and down. The pitch doesn't change, but the level meter becomes useless, and attack transients get exaggerated.
Low-frequency rolloff. Small mic, small diaphragm, physics. Under roughly 80 Hz your phone captures mostly the overtones of a note rather than its fundamental. A bass low E is 41 Hz; what the mic actually delivers is the 82 Hz and 123 Hz harmonics above it.
A good web detector asks the browser to switch the first two off, and the honest ones show you whether the phone obeyed — this one has a device report panel that tells you exactly that. The third is hardware. No software fixes a 6 mm diaphragm.
1 – Use the bottom mic and don't cover it. On most phones the primary mic is next to the charging port. A thick case or a finger over it costs you more accuracy than any algorithm choice.
2 – Hold the phone about 30 cm from the sound source. Touching the guitar body transmits handling noise straight into the reading.
3 – Watch the level meter, not your instinct. You want steady movement without the clipping warning. Red means back off.
4 – Tuning a bass? Read the caveat above and trust the detector's octave display with a grain of salt on the lowest string — if E1 shows as E2, the pitch class is still right, and that's what tuning needs.
Quiet room helps more than anything else on this list. Obviously. But it's the one people skip.
Installing the PWA takes ten seconds and means the tuner opens full-screen, instantly, with or without signal.
On Android Chrome: tap the three-dot menu, then Add to home screen, then Install.
On iPhone Safari: tap the share square, scroll a bit, tap Add to Home Screen. Apple hides it further down the sheet than Google does, but it's there.
After that it behaves like any tuner app. Except free, and 300 KB instead of 80 MB.