Another important sound commonly used in Rock and all its related styles is the use of both the minor and major third of a chord. There are literally thousands of sax, guitar and keyboard riffs which either alternate between the two thirds or begin on the minor third and then move to the major third.
Here is an example of this sound in the key of A. The minor (or flattened) 3rd is C and the major 3rd is C#. The notes of this solo come from a combination of the Blues scale (which contains the minor 3rd) and the A7 arpeggio (which contains the major 3rd).
Here is a 12 bar Blues solo in the key of Bb which makes use of many different intervals. Go through it and analyze the intervals and also the scale degrees against a Bb chromatic scale. Notice the use of both major and minor 3rd degrees, as well as the flattened 5th and 7th degrees of the scale. The b3, b5 and b7 are known as blue notes and are particularly common in Blues.