Filtering an audio signal & microphone question

So, I have a project in which I need to take an input of a monotone note, say for example an A with a frequency of 880Hz or another note using an electret microphone, and then use some filters to try to identify what the note was.
So I had an idea of using a bunch of filters in parallel each with different cutoff frequencies...and then checking the highest output (since this was the one that was less attenuated ... the signal must be of a frequency close to the cutoff frequency of that filter.... (I thought that the signal coming from the microphone would be constant
However I learned That a microphone's output is quite low and actually fluctuates between negative and positive peaks....
Therefore, I can't really attain an initial value which is stable, to know how much has been attenuated, and thus find out which filter that would correspond to.

Could anybody perhpaps enlighten me a bit further, are my assumptions correct??

You can do this entirely with analog electronics, using op amp bandpass filters.

You can also do this with an amplifier, the Arduino ADC and digital filters, but the Arduino is not fast enough to run several filters at the same time.

Finally, you can use an amplifier and 5 kHz low pass filter with the microphone, the Arduino ADC and either an FFT, FHT, autocorrelation or Goertzel algorithm to identify frequencies. Search this forum for some examples.

Yeah my goal is pretty much to do the thing by analog electronics....
but like the microphone produces AC sinusoidal voltage depending on the nature of the sound it receives right?
so being a sinusoidal voltage shouldn't it be changing constantly as the sound changes as well??
So imagine if the microphone produces a constant output of 400mV, and we amplify it to reach 2V approximately......
Using a filter to attenuate a small voltage such as 2V won't really produce a big voltage difference, so would I understand whether the signal was actually attenuated or rather just fluctuating due to the different sounds??

Thank you

What exactly are you trying to do? If the microphone is only exposed to the pure tones then I think what you are talking about should work. If the microphone is picking up background noise then the output will be changing all the time and will contain all frequencies. If the pure tones you are trying to detect are close together you can put a bandpass filter to reduce freq's above and below the range of interest. You can't really do anything to block noise in your range of interest once the mic picks it up. The best solution is to shield the mic from the noise and only expose it to the tones of interest.

For the low signal level you can either put a broadband amplifier on the output to increase the signal to the filters or add gain to the active filters you use to isolate the tones.