At age 84, Clint Eastwood is setting quite an example that people can stay as productive as ever well past the traditional retirement age. He’s been acting and directing at a rapid clip, and frankly doing some of the best work of his career in the past 20 years with movies like “Unforgiven,” “Gran Torino” and “Million Dollar Baby.”

The fact that he’s the director of the new Broadway musical adaptation “Jersey Boys” comes as a double surprise, then, as Eastwood is tackling an entirely new genre with this film. The guy who made his name playing macho icons in the “Dirty Harry” and “Every Which Way But Loose” movies is certainly not the first person one would expect to handle the story of guys who are singing and dancing, even if they are street thugs from early-1960s New Jersey.

Sadly, the fact that musicals are so foreign to Eastwood is perhaps its biggest downfall. Built around the dramatic true-life story of the rise and fall of Frankie Valli and the Four Seasons, who rode to huge success on the coattails of lead singer Valli’s improbably high-pitched vocals before collapsing in a mess due to massive financial misdoings by a fellow band member, “Boys” gets its serious moments right but never soars when it counts, during its musical moments.

The movie employs the clever narrative trick used in the stage play, in which each of the Four Seasons takes turns telling the story from their perspective. Frankie’s story starts when he’s a teenager, hanging around with thugs a couple years older who are always on the make, including a hilariously incompetent jewelry store robbery.  His best friend is Tommy DeVito, who helps him break out of his trap as a working-class neighborhood boy but ultimately betrays Frankie’s trust with his free-spending ways.

It’s obvious early on that Frankie has both star presence and that incredibly unique voice, pairing the two together to lead his thug buddies – who are also skilled rock musicians – into a record contract as a backup band and eventually rapid success with their own recordings. Frankie also uses his charm to entice an older beauty to seduce him and marry him – a relationship that brings him children as well as eventual heartache as he tours constantly to support them.

The movie takes at least a half-hour to kick into its first big rendition of a Valli song, but once the music starts it keeps coming in big waves. While the songs are undeniably fun to watch and hear again, Eastwood doesn’t present them with the pizzazz one might expect after a decade of high-energy, high-gloss musicals as “Chicago.” Instead, he seems to plant the camera in front of the band and make viewers feel like they’re watching the band play in mostly static position for early-era TV cameras.

The movie does better with its non-music scenes, as the young actors playing the musical icons give impressively wide-ranging performances that score points both with the sarcastic brotherly banter dispensed among the band members and with the more serious and even tragic moments that occur in the film’s second half. The fact that Eastwood chose to hire mostly-unknown actors rather than movie stars in the roles also lends a credibility to the film even as it likely lessens the fun. John Lloyd Young and Vincent Piazza are especially strong as Frankie and Tommy, giving both a sense of their youthful dreams and the anger involved in their fumbling them. When one considers that Young not only matches Valli’s look, handles an impressive spectrum of emotions and even pulls off replicating Valli’s voice, it’s an incredible feat.

“Jersey Boys” is rated R almost exclusively for its foul language. There’s a large number of F and A words, and quite a bit of using God’s name in vain, particularly in the form of GD and JC. But in the context of tough-talking street kids from early-‘60s Jersey, it doesn’t truly register as offensively as modern stories with the same kind of language issues, because history has already proven these kinds of guys really talked this way. There are implied affairs and one scene in particular fades in and out of a fellow band member losing his virginity to a hooker who’s provided to him as his “Christmas present,” but nothing sexual is shown.  

Overall, “Jersey Boys” is pleasant enough and has enough compelling drama to be worthwhile viewing for fans of the Four Seasons or their musical era. But what should have been musical magic instead is a well-produced story with its feet firmly in place rather than dancing across the screen.