Erik Peyton and Dan Van Why in Big Fish at Keegan Theatre. (Mike Kozemchak)

A bittersweet story about family dynamics. A slew of wild fables about a witch, a human cannonball, and more. The two narrative modes are sides of a single coin in “Big Fish,” a musical about a son’s relationship with his charming, infuriating fabulist of a father. Whether you consider the coin a matter-of-fact dime or a doubloon from a dragon’s hoard, it has been a good investment for the Keegan Theatre, whose generally agreeable “Big Fish” is billed as the musical’s Washington premiere.

With a score and lyrics by Andrew Lippa (“The Addams Family,” “I Am Harvey Milk”) and a book by John August, “Big Fish” draws on Daniel Wallace’s novel and its movie adaptation (for which August wrote the screenplay). Seen on Broadway in 2013, the musical tells of Edward Bloom, an Alabama-based traveling salesman prone to relating improbable yarns about his own past. His whoppers alienate his son, Will, but upon becoming a parent himself, Will puts exasperation aside in a search for the truth behind his dad’s fictions.

Co-directors Mark A. Rhea and Colin Smith have funneled a satisfactory amount of movement, humor, color and poignancy into Keegan’s “Big Fish.” The casting helps: In a role that takes Edward from a child to an old man, Dan Van Why creates a likable, if not transfixing, portrait of an audacious optimist; and Ricky Drummond makes Will appealingly flustered and vulnerable.

Those two actors sing well enough, but the show’s vocal high points arrive courtesy of Eleanor J. Todd and Katie McManus. As Edward’s patient and insightful wife, Sandra, Todd sounds terrific in the resigned love song “I Don’t Need a Roof,” as well as in the more upbeat “Magic in the Man.”

As the enigmatic and feisty Witch — whose encounter with the young Edward may be the key to understanding his later escapades — McManus delivers a knockout interpretation of the early number “The Witch.” This sequence, which features backup sorceresses in black capes like swirling bat wings, is impressively mysterious and dynamic, thanks to choreographer Rachel Leigh Dolan and costume designer Debra Kim Sivigny.

Also providing a signal contribution to the show is Patrick Lord, who designed the photographic and animated projections that help transform the stage — flanked with sheetlike, vine-patterned drapes — into the epic landscape of Edward’s inventions (a fairy-tale river, a dragon-haunted castle, etc.) as well as naturalistic locales.

With some pitch problems and a lack of mellifluous blending, the offstage band was not an asset at the press-opening performance. No other aspect of the production was such a letdown, although some scenes featuring full-cast tableaus looked awkward and planted.

Performer Grant Saunders makes a striking-looking giant; and Patrick M. Doneghy is pleasantly eccentric as circus impresario Amos Calloway (although his singing of certain lyrics sounded muddy). Emily Madden turns in a now-funny, now-touching portrait of Edward’s old acquaintance Jenny Hill — who helps us see that Edward’s foibles are also qualities that bring out the best in other people.

Big Fish. Book by John August; music and lyrics by Andrew Lippa. Directed by Mark A. Rhea and Colin Smith; scenic design, Matthew Keenan; lighting, Allan Weeks; sound, Tony Angelini; properties, Cindy Jacobs; musical direction, Jake Null. With Eitan Mazia; Courtney Moran; Allie O’Donnell; Erik Peyton; Molly Rumberger; and Rick Westerkamp. About 2½ hours. Through Sept. 9 at Keegan Theatre, 1742 Church St. NW. Tickets $45-$55. Call 202-265-3767 or visit keegantheatre.com.