A good start, but the useful tuner modes are in-app purchases.

To developer: Clicking speaker icons usually causes mute-unmute behaviour—not panels to slide down. How about just have a button or triangle labelled “Tone Generator”, or make the whole window visible when you start the app? It’s not obvious that there’s a hidden panel that will appear, and not all users consider the tone generator to be a secondary function of this app. I got the app 90% for the tone generator, because that’s what I use the iOS version for.

Just a note to potential users: "Fine tuning mode" and "Historical tuning mode”, both clearly present in the screenshots and what make the tuner portion of this App most useful, are premium PAY add-ons.

RWM-bass about insTuner - Chromatic Tuner for Guitar, Ukulele and String Instruments, v1.2