i stalk so you don't have to
Alex Ross on Steve Reich's Piano Phase in the New Yorker:
The opening section uses only the notes E, F-sharp, B, C-sharp, and D, which, when run together in rapid patterns, suggest the key of B minor. Halfway in, the note A is added to the series, tilting the harmony toward A major. This small change never fails to have a brightening, energizing impact. Pieces like this can leave you happy for hours, like drugs without the mess.