Its name is esoteric, but the diatonic phrygian tetrachord is perhaps the most common sequence in music. WNYC's David Garland tells NPR's Arun Rath how those four notes crop up from baroque to rock.

Whether you mean to or not, you’ll almost inevitably work in a particular key when writing a song. You might decide “right, this will be in C minor,” or you might just string together a seemingly ...