Watch the Melodic Minor Blues online guitar lesson by Larry Carlton from 335 Blues
The melodic minor scale has such a unique sound, and sets up a wonderful tension for resolving to a I chord. Melodic minor is a natural minor scale with a minor 6th and major 7th in it. Check the tab for the notes of an F melodic minor, which I'm playing in these examples.
Here we're using melodic minor a half step above the V chord (or, as I explain in the clip, half step above any chord that's functioning as a V chord). If you're playing blues in A, the V chord is E - and a half step above that is F.
So one place to use the F melodic minor scale is over the V chord in an A blues. It has great impact and pulls the ear back very strongly to the I chord (in this case, A).
In Video 2 you'll hear the melodic minor scale put to work on an A minor blues. Listen for it, learn the solo and then experiment using the melodic minor in other progressions and grooves.