In the last 40 years, only five women 40 or older have had a number one single on the Billboard Hot 100.

Only one of them was African-American.

Most music fans might not know those bits of trivia, but Grace Davis, one of the main characters in “The High Note,” is all too aware of those harsh facts.

Played by Tracee Ellis Ross (whose mother, Diana Ross, is one of those women who never had a chart topper after her 30s), Grace is a pop / R&B icon who remains a concert draw but who’s only released live and greatest hits albums for the last decade.

Her label has no interest in releasing new music from her, and her manager (Ice Cube) just wants to keep on the road and playing the hits.

“People don’t go see Yankee Doodle Bruce Springsteen (and want to hear the new songs),” he tells her. “People want ‘Thunder Road’ and that’s what we’re going to give them.”

Artists don’t want to keep painting the same subject, directors don’t want to keep making the same movie, and Ross captures the struggle of a singer who believes she can make new music that audience want to hear. However, she’s hesitant to buck a system stacked against her and doesn’t want to jeopardize the lifestyle to which she’s become accustomed.

She’s a compelling character. Perhaps the biggest problem is that she’s a supporting one in “The High Note.”

The “A” story is about her personal assistant, Maggie (Dakota Johnson), a music nerd and unabashed Grace Davis fan who dreams of producing records, not catering to the diva-esque whims of her employer.

But if the music business isn’t kind to women of a certain age, its track record with female producers (especially those who didn’t start as singers or songwriters) probably is worse.

Even after she does an impressive mix on Grace’s latest live album, her manager makes it clear that if she wants a successful career, she needs to find a new talent.

Maggie finds that in David Cliff (Kelvin Harrison Jr.), who she hears singing outside of a grocery store. She hides her producing side gig from Grace and convinces David she is an in-demand producer, not a personal assistant. Juggling two jobs ultimately endangers both.

“The High Note” is directed by Nisha Ganatra and has some surface similarities with her last film, “Late Night.” Both are about younger women working for demanding, established females who still are fighting their own battles about sexism in the entertainment industry.

Also like “Late Night,” “The High Note” is an easy watch, a flawed but entertaining film that coasts along so well on its mix of humor and the charm of its cast that its contrivances are easy to overlook.

The screenplay by Flora Greeson is filled with music-inspired banter and one-liners. Maggie disses “Hotel California” to David, calling The Eagles hokey and Don Henley mean, and describes one of David’s expensive jackets as looking like “Stevie Nicks ran over Jason Derulo with her car.”

DJ / producer Diplo has a funny scene as an arrogant DJ / producer brought in to modernize Grace’s sound. And the movie is effective in creating early “hits” for Grace Davis, heard in the concert sequences, that are convincing as pop hits from a decade or two ago.

Harrison has an appealing voice, but the songs he and Maggie create are less convincing as future hits.

In addition to handling the music, Ross pulls off the difficult balancing act of doing increasingly outrageous things to show how unsatisfying the job of personal assistant is for Maggie without losing the good will of the audience.

Johnson is fine as Maggie, but nearly all of the high notes here come when Ross is on screen.