Noteworthy Tuner is a chromatic instrument tuner for Android. As far as I can tell, it is the very first tuner that is both free and ad free (all other tuners I found required purchase to eliminate ads). It is also the first open-source tuner for Android. It is intentionally very simple. Just open it up and tune away!
• Instrument tuner for: guitar, ukulele (uke), violin, viola, cello, bass, and any other instrument
• Simple to use
• Detects note (no need to pick the note first)
• Chromatic (not just some specific notes, but all 12 pitches in the octave)
• Both free and ad free (no ads!)
• Open source