LED Music Visualiser
In addition to seconding the FFT approach, I'd like to point out why the F-V approach is problematic.  The circuit you linked to (and F-V circuits in general) depend on having a single-frequency input.  That is most definitely not a description of most music.  About the only thing it would work for would be solos of certain instruments that have repeating waveforms.  That rules out pianos, guitars, and all other plucked or struck string instruments (for example) since their &quot;harmonics&quot; are not true integer multiples of the fundamental during most of the note.  This means you can't extract the fundamental from the waveform to drive the F-V using any simple method.  (Or even any not-so-simple.)  And of course solo instruments have only minor parts in most music.  Yes, the guy in the YouTube got his LEDs to light up, but that doesn't mean he was visualizing the music in any but the crudest sense.