Android's volume slider has a floor, and on a lot of devices that floor is louder than it should be. The first step above mute is a fixed fraction of the device's maximum output, not a fixed loudness, so a phone or tablet with a loud maximum can leave you with "off" and "too loud" as your only two options.
This is a common enough complaint that there's a small ecosystem of apps claiming to fix it. Most of them don't, and the reason why is a genuinely interesting piece of Android audio API trivia. This post is about the one approach that actually works, why the popular alternative doesn't, and a separate engineering problem I hit while making the app that implements it buildable reproducibly for F-Droid.
I'm the author of under GPL-3.0, and available on . Full writeup of every other approach to this problem, including the ones that don't work, is in the companion guide.
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