This wah-wah solo can be found on my band Artifex's latest demo - a song called "Alley cats". It is cool because it revolves around a single riff in E. Since there aren't any chord changes to rely on - the solo needs other qualities than the harmonic ones. Therefore, I focused on crazy sounding wah-wah licks, rhythmic ideas and MIGHTY SLIPPERS . Once again, this is a way to make a cool solo without relying on strong chord notes. The solo reaches it's peak with an exotic/progressive sounding phrase which I play in unison with my drummer and bass player.
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Backing Riff
There is no obvious "tonic center" (key) in this riff. However, the notes of the solo revolve around E minor.
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Eminor scale twelve positions (Red dots = root notes ):