"Yes, basically, like you said, I'll work out a chord pattern and work out the lyrics over that"

This quote by Roger McGuinn is referring to the procedure of songwriting. He is stating that he will begin by producing a chord pattern, which is the musical structure of the tune. Then he will exercise the lyrics over that chord pattern. This is a typical technique to songwriting, as the chords offer the structure and the tune for the tune, and the lyrics are then written to fit the tune. By exercising the chord pattern first, McGuinn is making sure that the song will have a strong structure and that the lyrics will fit the tune. This technique is typically utilized by skilled songwriters, as it permits them to create a tune that is both musically and lyrically strong.