Grumpy_Mike:
You're not going to get that by decoding a $20 tuner either
Wouldn't be so sure, don't forget that you pay for software once only, with hardware you pay every time.Detecting a note can be difficult because of the harmonic content, notice that tuners do not always give the octave but just the note. It is a mistake to think that the fundamental is always the largest harmonic or the lowest harmonic.
Yes, but to what purpose, and by what means? The tuner accepts analog-in. That can be controlled by a generator(s). Then inside the chip is 'mystery software' (the software that the OP wants to 'do better' than.) Then LCD-out. The only possible way to perform the exercise is to know, down to the nth detail, exactly what's going into it tuner, and then watch how it displays. With that, yes, one could figure out at least what 'kind' of analysis it's doing to find frequency/octave/whatever. However, the only way to do that kind of analysis, again with nothing more than audio input, with the high-end hardware, and an LCD output is to already -know- how to do what the chip is doing in the way of audio analysis. A class-A (just for reference) engineer -could- do that kind of analysis on any device, because he already knows every algorithm. By the behavior of the output as compared to the input he'd 'know' what the software was doing. But for an 'I have an Arduino' newbie, it's simply purely absolutely impossible to learn anything, other than how to decode LCD signals.
By analogy, it's like putting a car on jacks, starting the car and putting it in gear, watching the wheels spin around, and trying to 'analyze' the fuel injection and ignition systems, to build a better motor that improves mileage.
Don't get me wrong! I'm NOT saying that OP CAN'T build a better trapper-of-mice, only that 'decoding an LCD' is the -completely- wrong way to go about it.