I also made and released a chromatic instrument tuner using web audio input a while back:<p><a href="http://www.leshylabs.com/apps/tuner/" rel="nofollow">http://www.leshylabs.com/apps/tuner/</a><p>I haven't looked too closely, but my technique is probably a bit different. I use FFT only to gain a hint of where to look. FFT itself, at least in the form that is built into the web audio api, is not accurate enough for a tuner. Instead, after FFT tells me where to look, I use auto-correlation to scan those frequencies. I'm not sure if this is the ideal technique, but it seems to work pretty well.<p>I may have released too early, because back when I wrote this web audio input only worked in limited versions of Chrome. It didn't even work in the main release without changing flags, and so my release went mostly unnoticed on the internet.<p>I haven't checked in a few months, but I've been waiting for mobile support to catch up. Firefox mobile beta started somewhat working a few months ago, and I don't know if that moved up into the main version. While Chrome works well on the desktop now, on mobile I don't think they have any working web audio input support, unless that changed recently.