user60332: I'm wondering if Arduino is able to not just measure sound and work based on hearing a sound that is "loud enough", but if it is able to identify a specific sound (say the first few seconds of a song). Is this possible, and how would one go about doing so? 
If identifying the first few seconds of a song isn't really feasible, is it at least possible to do so with a consistent (but particular) pitch (rather than a general loudness threshold)?

user2967: It sounds like you need to do Fourier analysis on the sound. (Breaking up the sound into its component frequencies.) Most Arduinos are based on AVR chips, which do not have hardware support for floating point math. They use software to do floating point, which makes them a poor choice for this sort of thing.
There are FFT libraries for Arduino, but they will be slow and fairly crude. You'd probably be better off using a board like a Raspberry Pi that has an ARM processor for signal processing like this. 

user7508: As stated in other answers, sound recognition is completely out of the
realm of what an Arduino can do, but recognizing a specific pitch is
possible.
However, contrary to previous answers, I would recommend against using
an FFT. The FFT is the right tool when you need to get all the
frequency components. It is, however, overkill when you want to look at
a single frequency. Given the low processing power at your disposal, I
suggest you try instead an homodyne detection scheme. An Arduino
Uno, or similar board, has enough resources to sample an input at
9.6 kHz, and extract in real time a specific frequency component.
See for example this homodyne detection program.

60332: <p>I'm wondering if Arduino is able to not just measure sound and work based on hearing a sound that is "loud enough", but if it is able to identify a specific sound (say the first few seconds of a song). Is this possible, and how would one go about doing so? </p>

<p>If identifying the first few seconds of a song isn't really feasible, is it at least possible to do so with a consistent (but particular) pitch (rather than a general loudness threshold)?</p>
 2967: <p>It sounds like you need to do Fourier analysis on the sound. (Breaking up the sound into its component frequencies.) Most Arduinos are based on AVR chips, which do not have hardware support for floating point math. They use software to do floating point, which makes them a poor choice for this sort of thing.</p>

<p>There are FFT libraries for Arduino, but they will be slow and fairly crude. You'd probably be better off using a board like a Raspberry Pi that has an ARM processor for signal processing like this. </p>
 7508: <p>As stated in other answers, sound recognition is completely out of the
realm of what an Arduino can do, but recognizing a specific pitch is
possible.</p>
<p>However, contrary to previous answers, I would recommend <em>against</em> using
an FFT. The FFT is the right tool when you need to get <em>all</em> the
frequency components. It is, however, overkill when you want to look at
a single frequency. Given the low processing power at your disposal, I
suggest you try instead an <a href="https://en.wikipedia.org/wiki/Homodyne_detection" rel="nofollow noreferrer">homodyne detection</a> scheme. An Arduino
Uno, or similar board, has enough resources to sample an input at
9.6 kHz, and extract in real time a specific frequency component.
See for example this <a href="https://gist.github.com/edgar-bonet/0b03735d70366bc05fc6" rel="nofollow noreferrer">homodyne detection program</a>.</p>
