The 9th (D) is nine notes above the original root when we play a two-octave C major scale. This, plus the inclusion of the b7 (Bb), is why this chord is called C9, instead of Cadd9.

Joe Satriani, Eric Johnson, Eric Clapton and Randy Rhoads all used this fundamental guitar mode in their songs. Here, Stuart Ryan takes you through the basics of the Ionian mode and shows you how to ...