As you already know, intervals add variety to lead playing. Once again, take a look at the animated gif below. This is an example of pedal point. The lick "bounces" off the red note which is an "A" in the key of "A". Every other note to be played is the "A". This is most often used in classical music, but, as evidenced here, it can work in other genres as well. When visualizing this lick, think of the notes that comprise the minor pentatonic. This lick also sounds best when fingerpicked or, if you perfer to keep your pick in hand, hybrid fingerpicked.
When two notes are played in unison, it is referred to as a "Double Stop". You can hear this idea extensively throughout many Blues players styles. The intervals of the double stops are major 3rds. The two notes that make up the double stop can be fretted with your index finger and ring finger alternately. Try simulating a minature barre chord. Have fun!
Click the ear to hear this lesson incorporated into an audio sample...