Lawrence Lowell Williams was born in Kansas City, Kansas, and grew up in Overland Park, Kansas. He started on clarinet at eight, following his father, a saxophonist. He studied at New Mexico State University and in 1969 moved to the Indiana University School of Music, where he played with visiting orchestras led by Glen Campbell, Henry Mancini and Johnny Mathis. His own website describes the Indiana years as a music scholarship covering classical and jazz study. No birth year is publicly documented.

The decisive meeting at Indiana was with the trumpeter Jerry Hey and the saxophonist and flutist Kim Hutchcroft. Williams has said the three hit it off in 1969 over a shared taste for R&B, jazz, funk and improvising, and that they modeled their horn-section writing on Tower of Power, Edgar Winter's White Trash, James Brown, Chicago and Blood, Sweat & Tears. They left for Hawaii with other Indiana players and formed Seawind, the jazz-fusion band with which Williams first recorded. Seawind began as a club and dance group with no original material, then moved to originals, with Pauline Wilson singing and her husband Bob Wilson on drums and writing. The horn trio, billed as the Seawind Horns, drew the attention of the drummer-producer Harvey Mason, who urged the band to relocate to Los Angeles, where it took a regular engagement at The Baked Potato.

Seawind's first album, Seawind (CTI, 1976), shows how much of the band Williams was. Discogs credits him with acoustic piano, Fender Rhodes, several ARP and Oberheim synthesizers, clavinet, alto and tenor saxophones, alto flute and vocals, plus a tenor solo on "You Gotta Be Willin' To Lose (Part II)" and the horn arrangement of "The Devil Is a Liar." That song earned the band a 1978 Grammy nomination for Best Arrangement Accompanying Vocalist(s). Window of a Child (CTI, 1977) reached No. 122 on the Billboard 200 and No. 55 on the R&B chart, with Williams on keyboards and woodwinds and arranging the strings. Light the Light (Horizon, 1979) peaked at No. 143, and Seawind (A&M, 1980) at No. 83 and No. 20 on the R&B chart, with "What Cha Doin'" reaching No. 18 on the R&B singles chart. The group disbanded in 1982, which Williams has attributed to the end of the Wilsons' marriage; he has said the band kept going for a few years without a singer, but it was not the same.

Quincy Jones had noticed the band in Los Angeles, and Williams, Hey and Hutchcroft became studio players for Jones and the artists he produced, among them George Benson, the Brothers Johnson and Michael Jackson. Williams has said his first Jackson session was for the soundtrack to The Wiz, which Jones arranged; he then played on Off the Wall (1979), where Discogs credits him with alto and tenor saxophones and flute on nine tracks and the alto saxophone solo on "Girlfriend," and on Thriller (1982), Bad (1987) and HIStory (1995). On Thriller he is credited with tenor saxophone, flute and keyboards, and on Bad he plays keyboards and takes the saxophone-synthesizer solo on "Speed Demon," after what he has described as many months of drum programming, keyboard and horn work on that record. For Quincy Jones himself he is credited on The Dude (1981), where Discogs lists saxophone and flute on the title track, and on Back on the Block (1989) and Q's Jook Joint (1995). His website counts more than 30 projects with Jones, whom it names as his mentor.

The same Los Angeles session circle carried him through the jazz-fusion and crossover records of the late 1970s and 1980s. He appears on Earl Klugh's Finger Paintings (1977), Harvey Mason's Earthmover (1976) and Funk in a Mason Jar (1977), Lee Ritenour's Feel the Night (1979) and Rit/2 (1982), George Duke's Follow the Rainbow (1979), A Brazilian Love Affair (1980) and Dream On (1982), Alphonse Mouzon's By All Means (1981), Herbie Hancock's Lite Me Up (1982) and Spyro Gyra's Incognito (1982). The Seawind players also served as the backing band on the Japanese saxophonist Toshiyuki Honda's debut, Burnin' Waves (1978), with Williams on keyboards.

Much of his catalog sits outside jazz, and it is large. Among the pop, rock and R&B records he is credited on are Barbra Streisand's Songbird (1978), Dolly Parton's Heartbreaker (1978), Elton John's 21 at 33 (1980), Joni Mitchell's Wild Things Run Fast (1982) and a long list of Rufus and Chaka Khan, Pat Benatar, Simply Red, Rick Astley and Sheena Easton albums. He is also reported to have played the saxophone solo on Sheila E.'s "The Glamorous Life" (1984). His website puts the total at over 2,000 records, films and commercials. The jazz thread in all of it is Al Jarreau.

Williams first appears on Jarreau's All Fly Home (1978) as an additional keyboard and synthesizer player, and he toured and recorded with him for more than three decades, often handling his arrangements. He is credited with synthesizer on This Time (1980) and Breakin' Away (1981), keyboards and woodwinds on Tomorrow Today (1999), and keyboards on four tracks and flute on one of All I Got (2002). On Accentuate the Positive (GRP, 2004), produced by Tommy LiPuma, he played keyboards and wrote the arrangements for eight of the eleven tracks, among them "The Nearness of You," "My Foolish Heart," "Waltz for Debby" and "Groovin' High," and the album received a Best Jazz Vocal Album nomination at the 2005 Grammy Awards. Jarreau said in a 2004 JazzTimes interview that Williams knew him so well that arranging the record was the natural choice. On Givin' It Up (Concord, 2006), the duet album with George Benson, Williams is credited with keyboards and arrangements on several tracks, including "Breezin'" and "Summer Breeze," and with a co-producer credit on "Every Time You Go Away." Jarreau passed away on February 12, 2017, and Williams has since appeared in Jarreau tribute concerts, according to his website.

His only record under his own billing is The Beautiful Struggle (Sony Music Japan, 2001), credited to Larry Williams & Friends. Williams plays piano, synthesizer, tenor saxophone and alto flute, arranged and produced it, and engineered it at his own Willyworld Studio. He has said Sony paid him and gave him full artistic freedom, and that he is not driven to be a leader, preferring a small part in a great production to leading an average one. Seawind regrouped for a Los Angeles concert in 2005 and released the new album Reunion in 2009. His website's activity list runs into 2025 and includes a saxophone solo with Samara Joy at Quincy Jones's 90th birthday celebration in 2023, saxophone on the 67th Grammy Awards telecast in 2025, and the score for a feature film, Love After, begun in 2024.

Williams is a session musician and arranger first, and most of what he has recorded is pop, R&B and rock, made for artists far outside jazz. The jazz identity comes from where he started and who he kept working with: a fusion band that recorded for CTI, a place in the Quincy Jones circle that produced the Lee Ritenour, George Duke, Earl Klugh and Harvey Mason dates of the late 1970s, and three decades beside Al Jarreau. Asked to name a favorite style, he picks progressive jazz as the most demanding, while saying he likes almost any style done at a high level.

What he brings is range under a single pair of hands. Discogs lists him on keyboards, synthesizers, piano, tenor and alto saxophone, flute, alto flute and piccolo, with arranging credits for horns and strings. The horn-section sound he helped build with Jerry Hey and Kim Hutchcroft, tight and bright and shaped by the Tower of Power and Chicago model, ran through the Quincy Jones productions of the period. Jarreau's own explanation in 2004 for handing him the arrangements, that Williams knew his history, his tastes and his stage self, describes the long partnership better than any chart position.