Joni Mitchell was ready for a change in 1973. Jilted by James Taylor in 1971 in favor of Carly Simon, Ms. Mitchell began a romantic relationship with Jackson Browne in 1972 that also ended badly. After releasing "For the Roses," her follow-up album to "Blue," late that year, Ms. Mitchell spent much of 1973 working on her next album. Weary of folk's limited instrumentation, Ms. Mitchell chose to widen her music's scope with a more sophisticated sound. She decided on jazz.

In the summer of 1973, Ms. Mitchell hired the L.A. Express, a jazz-rock group of studio musicians, to back her in the studio. She had its leader, Tom Scott, who played on "For the Roses," arrange the instrumental and orchestral accompaniment. When "Court and Spark," her sixth studio album, came out 50 years ago this month, Ms. Mitchell's voice and songs were invigorated by a new jazzy backdrop tailored to her approach. Her vocals still soared majestically and delivered lyrics breathlessly, but now the L.A. Express and Mr. Scott's arrangements gave her songs a new dimension.

The record sold 500,000 copies just over a month after its release and peaked at No. 2 on Billboard's Hot 200 chart for four weeks. The single "Help Me" climbed to No. 7 and became her biggest career hit, and Ms. Mitchell and Mr. Scott shared the Grammy for Best Arrangement Accompanying a Vocalist for the song "Down to You." The LP was inducted into the Grammy Hall of Fame in 2004.

The album's songs about lust and love, flawed romantic partners, unfulfilled partygoers, disappointment and depression connected deeply with listeners. Ms. Mitchell's fearless plunge into her heartbreak and confusion influenced multiple generations of female singer-songwriters, including Stevie Nicks, Tori Amos, Alanis Morissette, Sheryl Crow, Billie Eilish and Taylor Swift.

The collaboration on the record began with Mr. Scott listening to tapes of Ms. Mitchell playing and singing the songs. Then he transcribed them for the L.A. Express to record basic rhythm tracks. "Joni and I listened and discussed her desired instrumentation," he said in a phone call in late December. "When Joni and the band recorded together, the musicians were free to react to the mood of her vocals and lyrics."

Ms. Mitchell's solo piano opens the title track, which grapples with a lost romantic suitor and her unwillingness to sacrifice her West Coast life: "And the more he talked to me, you know / The more he reached me / But I couldn't let go of L.A. / City of the fallen angels." Larry Carlton's meowing electric guitar echoes her puzzlement and regrets.

"Help Me" is still one of the most eloquent songs about rushing headlong into a one-sided relationship: "Help me, I think I'm fallin' in love with you / Are you gonna let me go there by myself? / That's such a lonely thing to do." Mr. Scott's flute and baritone sax, Mr. Carlton's guitar, Joe Sample's electric piano and the background vocals echo her sentiments with slick and brittle textures.

An early-1970s trip Ms. Mitchell took to France with her agent and friend, David Geffen, and The Band's Robbie Robertson and his wife, Dominique, was the inspiration for "Free Man in Paris." The song is sung from Mr. Geffen's perspective, liberated from work worries. David Crosby and Graham Nash join on background vocals.

"People's Parties" is an observational account of a gathering following Carole King's Central Park concert in May 1973, Mr. Scott said, where emotions ran high and low. Ms. Mitchell struggles to process the laughter and crying: "I'm just living on nerves and feelings / With a weak and a lazy mind / And coming to people's parties / Fumbling deaf, dumb and blind."

Ms. Mitchell's search for love and incomprehension over male behavior continues with "The Same Situation" and "Car on a Hill." The album's most orchestral work, "Down to You," includes Ms. Mitchell's fascinating piano chord voicings joined by Mr. Scott's whispering orchestral strings and supportive woodwinds and French horn. Here, she explores the loneliness of desire without love.

"Just Like This Train" is another gem awash in bright instrumental riffs and soft jazz. Here, Ms. Mitchell takes herself to task for boarding the metaphoric train of temptation and losing her heart. "Raised on Robbery" features Mr. Robertson on electric guitar and a wailing sax solo by Mr. Scott.

A soulful arrangement supports "Trouble Child," Ms. Mitchell's sympathetic look at women who succumb to male dominance and find they are unable to truly love. The closer, "Twisted," was a 1949 solo by tenor saxophonist Wardell Gray with lyrics added by Annie Ross in 1952 that push back on psychoanalysts who think eccentric, emotional women are nuts.

"Court and Spark" is a wondrous journey through the lovelorn life of an exceptional singer-songwriter. The album is richer for Mr. Scott's sensitive arrangements and the L.A. Express's empathetic touches.