“Tell Tale Signs,” the latest installment of Bob Dylan’s “Bootleg Series,” provides a tantalizing glimpse into the songwriting process of this most elusive of musicians. The two-disk set (or three-disk, for an extra $100) includes unreleased songs, alternate versions and live recordings from the years 1989 to 2006, a period of great critical and popular success for Dylan.

As Dylan has become more and more the inscrutable, grizzled legend of today, there has been a desire to reify his songs, to see them as a part of nature. We imagine them springing fully formed from his brain. Whether or not this happened at one point in his career, “Tell Tale Signs” shows us another, very different side of Bob Dylan.

As an older man he proves to be an indefatigable studio experimenter, willing to explore the emotional resonances his lyrics take on in different musical settings. It’s fascinating to hear songs you’ve lived with for years in embryo. The rueful irony (or vacillation) of “Most of the Time” may seem utterly inevitable to us now. But “Tell Tale Signs” gives us two early versions in which we see the song incrementally acquiring its meaning. The three versions of the song “Mississippi” have a subtlety and strangeness that the album cut lacks. Not that they are necessarily better. But our conception of the song is now three times broader.

The overall sense you get is that these songs aren’t static and dead, the way we conceive of most pop music. When you hear a Bon Jovi tune on the radio, it’s always the same. It’s dead, it’s just data. There’s nothing real about it. I guarantee you it sounds identical when he plays it in concert. His fans get off on this fact of repeatability. They’re getting what they paid for. They can go home satisfied. A Dylan song isn’t like that. It’s only the way it is by accident. It just happened to be captured on a particular day in the studio. His songs are continuously evolving. If you listen to “Tell Tale Signs” enough, your conception of pop music starts to change. You begin to hear songs as drafts, as works in progress. They begin to have some relation to the highs and lows, the mind, of an actual human being.