[jvm___]

If you strum an electric guitar and let the hertz of the string fall through the range of AM radio the amp will briefly pickup AM radio stations. Not that you can decipher anything but you recognize voices as it travels past the station.

[jacquesm]

That's not because of the frequency of the guitar but because the guitar functions as a very nice antenna (long piece of metal (the strong) + a coil forming a tuned circuit), what happens is that your hands create a very temporary partial diode where you touch the strings!

Such naturally occurring diodes are an interesting phenomenon (in this case: the salt in your sweat interacting with the steel of the strings) and were the basis of the very first radio receivers after the 'Coherer' (which is a word that has fallen out of use so far that it registers as a spelling error on my browser!).

[nicolaslem]

That may be one explanation, but more broadly with analog audio it is actually quite difficult NOT to end up with an AM receiver.

[jacquesm]

Too late to edit: strong => strings. sorry!

[bonzini]

How so? A guitar doesn't go past a few kHz (the highest string is IIRC 660 Hz, and the top fret is 660*4) and AM long wave radio—which is almost dead—starts around 120 kHz.