Introduction
This is a simple slide solo in Em Pentatonic. The Pentatonic scale is simply a Major scale with two notes missing, the fourth and seventh degrees. The relative Major scale to Em is G Major (they share the same key signature). The two notes that are missing from G Major-Em are C and F sharp:
G Major-Em
G A B C D E F sharp G
G Major-Em Pentatonic
G A B D E G
The solo deviates from the Em Pentatonic scale in some measures. When playing across the A7, I have used chord tones: A (root note of A Major) and C sharp (the third of A Major). Measures two and four include the third degree of E Major: G sharp. Slide players incorporate these chord tones all the time, simply because they allow the slide to remain straight across the fretboard, and they sound great! The turnaround (the last two measures) consist of a very common chromatic (one fret at a time) run, up to the desired B. The twelve bar format usually ends on the 'five' chord, in this case B7, when leading back to the beginning. If you are at the end of the piece, end on the 'one' chord, in this case E7.
Performance
Play the piece throughout with the slide, that is, there are no fretted notes. Slide into the first note of each measure. Muting behind the slide with the fret hand is essential, cutting off any unwanted extraneous tones. Don't lift your fret hand off the strings behind the slide. Every note should sound clean, without them all ringing together. This will sound mushy with even a small amount of distortion.