Ask Al Stewart to sum up where he is now, musically speaking, and you’re likely to wind up two steps behind where you started; this is by no means an unusual circumstance in conversation with Al, keenly aware as he is that making a leap forward often entails taking a step backward. Sometimes it’s into the library stacks where the late historian Ms. Tuchman dug for material. Sometimes it’s into the record stacks where the late rocker Mr. Cochran made his mark as a teenager singing his “Summertime Blues” so many summertime’s ago. Al Stewart came to stardom as part of the legendary British folk revival in the sixties and seventies and developed the combination of folk-rock songs with delicately woven tales of the great characters and events from history.