In the world of professional theatre, things can change up until the very last minute. Before Broadway musicals officially open, they undergo an extensive process called previews. For actors and producers, these previews are a chance to test and fine-tune the show in front of a live audience. And for those audiences, they’re a rare glimpse into theatre’s creative process—often for a much cheaper ticket price. Here’s all the reasons why theatre fans should check out Broadway previews before they hit the Great White Way:

It might be a lot closer to home

In the past, shows destined for a run on Broadway would spend months on the road, ironing out the kinks. Things are a little less itinerant nowadays, but out-of-town tryouts still happen in major cities throughout the U.S. Chicago audiences saw On Your Feet well before it became a hot ticket in New York. More recently, Boston-area audiences got a glimpse of Waitress in its extended run at American Repertory Theatre in Cambridge. You never know when the show down the street is on its way to some big victories at the Tony Awards.

Some songs may never be heard again

In many cases—especially those out-out-town tryouts—musicals see some dramatic changes while still in previews, and sometimes that comes in the form of new or vanishing songs. Stephen Sondheim famously changed up the score for Follies before it opened at the Belasco Theatre, exchanging the wonderful “Can That Boy Foxtrot?” for the now-iconic “I’m Still Here.” Before it premiered at what is now the Richard Rodgers Theatre, Chicago made an even bigger change: not only did “Ten Percent” get the ax, but the entire character who sang it did as well.

Technical glitches are a fun surprise (and may cost you nothing)

It’s not just the librettist and composer who make fixes before opening. Imagine seeing Les Misérables with a barricade malfunction, Phantom of the Opera with a chandelier that doesn’t fall, or Avenue Q with puppets whose mouths don’t open. Don’t worry, though—if the show can’t go on, theaters traditionally offer tickets to another showtime.

You can see the show for the first time—a second time

A preview performance offers a perspective few people—other than the cast and crew—ever enjoy. And it gets even better if you attend the show’s official performance, too. Comparing and contrasting the two versions opens up a window into the creative process, giving audiences a chance to appreciate the impact an added joke, excised scene, or new cast member can have on the show’s success.

Like it before it’s cool… or before it disappears

Previews are an opportunity to fall in love with something before it reaches the culture at large. There are only a handful of theatregoers out there who can honestly say they saw Hamilton before it was cool, or who got to hear The Book of Mormon at the Eugene O’Neill Theater before almost anyone else. And fewer still got to see the legendary flops (Carrie, anyone?) before they shuttered. But whether the show’s a flop or a hit, the fact that you got to see it early could be a once-in-a-lifetime experience.