From my upcoming review in The American Conservative:
Musicals won six Best Picture Oscars in the 1950s and 1960s, but only one since ("
Common as this criticism is, it's a rather unpersuasive explanation because we remain perfectly happy with many other implausible artistic conventions. We seldom scoff that a novel's omniscient third person narrator presumes a point of view that only God enjoys; that stage plays are ridiculous because normal people don't converse in complete sentences while all facing toward an invisible fourth wall; or that, unlike in sitcoms, families don't actually sit around in vast living rooms cracking wise.
If lack of realism truly is the cause of the musical's decline, then "Once," a tiny Irish musical written and directed by John Carney, should win box office success comparable to the enthusiasm it has inspired in critics. "Once" overcomes this common objection by giving its hero (played by an oversized red-headed teddy bear named Glen Hansard, the guitarist in the last Irish musical, 1991's "The Commitments") a practical reason to break into song on the sidewalk: he's a street musician who does indeed routinely pour out his heart, as battered as his old acoustic guitar, to the passing multitudes. So, the musical interludes in the film are perfectly plausible.