Music may be the food of love, but it’s also fuel for drama. Not even counting opera and musical theater, where it’s the main course, music provides everything from transition interludes to emotional accents to thematic underscores in any number of straight plays. The mysteries of musical genius from Amadeus to Satchmo have been explored on stage. Shakespeare’s plays are strewn with songs that amplify and punctuate the plot. Two prime examples of music shaping the character of a play presented themselves in a couple of shows I saw recently in Boston—shows that have nothing at all in common except that both of them are, excuse the expression, alive with the sound of music.

Music is the central theme of Moisés Kaufman’s 33 Variations, now playing at the Lyric Stage Company. It’s about Ludwig van Beethoven (James Andreassi), whose late-life obsession with a mediocre waltz tune composed by his music publisher, Anton Diabelli, led him to create 33 piano variations on it. And simultaneously, it’s about a fictional modern-day musicologist, Katherine Brandt (Paula Plum), who’s obsessed with discovering the roots of Beethoven’s obsession.

As Beethoven argues with Diabelli, who is impatient to publish the ever-growing, apparently never-ending collection of variations, Brandt bickers with her adult daughter, whom she considers a dilettante. For both characters, there’s also a contrapuntal progression of loss. Beethoven is going deaf, while ALS (Lou Gehrig’s Disease) is gradually devastating Brandt’s physical faculties.

Throughout the play, which travels freely through time and space, we hear excerpts from the Diabelli Variations (including never-before-heard sketches), played onstage by pianist Catherine Stornetta. Music is not just the topic, but almost a character in this piece. The music unites the two characters and closes the 200-year gap between their lives. And as Beethoven’s manuscript pages are projected on a wall of the set, the notes fill the air of the theater—the musical “script” brought to life by performance.

The best-known thing about Shakespeare’s Two Gentlemen of Verona is a song, thanks to the musical setting by Beethoven’s contemporary Franz Schubert. This early, much-neglected play experiments with devices that pop up in Shakespeare’s later comedies: the mis-delivered letter, the girl disguised as a boy, the spurned lover pursuing her faithless beau, the laconic, self-mocking clown, the idiot would-be suitor.

“Who Is Sylvia” is the only song in the script, but in the Actors Shakespeare Project’s recent production there is hardly a music-free moment. The piece is packed with original music by Shakespeare & Company’s multi-talented Bill Barclay, who also played one of the two gents. An opening salsa-beat dance introduces the plot’s swirling exchange of letters and changing partners; a solo onstage guitarist, Max Kennedy, accentuates the action and segués the scene shifts; and the romantic serenade to lady Sylvia becomes a manic multi-instrumental production number out of the doo-wop era.

As in 33 Variations, the music is more than incidental. It’s a structural element—in this case, spurring the plot, upping the gag quotient and underpinning the style.•

Contact Chris Rohmann at StageStruck@crocker.com.