Modeling mathematical representation for music signal

[asifadio]

Hello there I am sorry if this sounds silly or out dated

i want to ask anyone, how can i model the mathematical representation from music signal(time domain).

lets say i recorded the signal from guitar through my music production software and print screen that signal as shown here upload.wikimedia.org/wikipedia/commons/4/4d/C_Envelope_follower.png

how do i model the mathematical representation for that graph? do i need to zoom in and separating that signal and find it one by one using piecewise function(since it is ADSR)?

or is there another way using computer software in signal processing to obtain the mathematical representation?

please help me
thanks

 

[fresh_42]

Look up Fourier transformations. This is a bigger chapter and cannot be answered quickly.