I am being asked to design a gadget that has some special features, but also includes a guitar tuner. I have looked at the web a bit, but not found any good references that show exactly how a tuner works. One paper I found talked about a rather complex "constant Q transform". I just don't think the $10 tuner I have uses anything that complex. I'm thinking they are doing a PLL sync to the input or something more like that.
One reference I found talks about using a peak detect to measure period rather than frequency like an FFT. I would think the FFT has too little resolution unless it is very long.
Anyone know how the commercial low end gadgets really work? Maybe I'll take mine apart, but my bet is they are using chip on board with the die under a dab of black goo.
Rick