Gregg Karukas was born on May 18, 1956, in Baltimore and grew up in Bowie, Maryland, where he played in the Bowie High School Starliners big band. According to his own biography he owned one of the first Minimoog synthesizers at sixteen, and after losing the tip of his right middle finger at twelve he kept practicing piano with four fingers until it healed. The same biography names his first record session: background Moog textures for the naturalist Euell Gibbons's readings of Henry David Thoreau, an album that Discogs dates to 1974. Through the late 1970s he worked in Washington, D.C., in jazz-fusion groups, spending five years in Tim Eyermann's band East Coast Offering and playing with the group Natural Bridge alongside the bassist Michael Manring, while jingle sessions taught him arranging, engineering and production.

He moved to Los Angeles in 1982 with, as he tells it, the aim of playing as many styles as possible rather than building a solo career. His first Los Angeles show came on his twelfth day in town, with the singer-songwriter Shelby Flint, and he soon toured with Melissa Manchester. His first major sessions were synthesizer and bass-line parts for Rockwell's "Somebody's Watching Me" (1984), the same year he added synthesizer to pianist Gene Harris's album Nature's Way, and he arranged and played the themes for Disney's DuckTales and Chip 'n Dale Rescue Rangers. Much of his television and film work was with the composer Craig Safan, including the underscore for Cheers and the film Stand and Deliver (1988), and he led the studio house band for It's Garry Shandling's Show on Showtime. He also played in the first lineup of the Rippingtons, the contemporary jazz group led by the guitarist Russ Freeman, and is credited with keyboards on its debut album Moonlighting, recorded in November 1985 and released in 1986 by Passport Jazz and GRP. His biography says he began touring with the original group in 1987.

His own records began that same year with The Nightowl (1987), issued on the Optimism label with the guitarist Ken Navarro and the saxophonist Gary Meek. Navarro executive-produced his next three albums for Positive Music: Key Witness and Sound of Emotion (both 1991, per Discogs) and Summerhouse (1993). Dave Koz, Eric Marienthal, the Brazilian composer Dori Caymmi and the guitarist Ricardo Silveira appear on Sound of Emotion, and Summerhouse adds Boney James and Everette Harp. A Christmas album with Flint, Home for the Holidays (1993), came out on his own Nightowl Records, followed by You'll Know It's Me (1995, Fahrenheit), Blue Touch (1998, i.e. Music), Nightshift (2000) and Heatwave (2002) on N-Coded Music, and then Looking Up (2005) and GK (2009) on Trippin 'N' Rhythm. Heatwave brought in Kirk Whalum, Koz and Rick Braun, and Looking Up featured Peter White. His website counts thirteen solo CDs across three decades.

Brazilian music runs through the other half of his career. His biography describes touring in the 1990s with Sérgio Mendes, Caymmi and Silveira as some of his favorite experiences, and it lists performances at Montreux with Caymmi and at the Hollywood Bowl with Ivan Lins, Oscar Castro-Neves, Antonio Carlos Jobim, Toots Thielemans, Mendes and Caymmi. He plays keyboards on at least six tracks of Caymmi's Kicking Cans (1993). Alongside that came a long run as a smooth jazz sideman and musical director, with Larry Carlton, Jeffrey Osborne, George Duke, Brenda Russell, Peter White and Boney James among the names Wikipedia and his biography list, and as a producer and arranger for others. David Lanz recommended him to the pianist Omar Akram, whose Free As A Bird (2004), Secret Journey (2007) and Echoes of Love (2012) he produced, arranged and largely co-wrote. Echoes of Love won the Grammy Award for Best New Age Album at the 55th Grammy Awards on February 10, 2013, and Karukas, credited as producer, arranger, engineer, co-writer and keyboardist, counts the award as his own. He also produced tracks on Lanz's Finding Paradise (2002) and The Good Life (2004) and co-wrote Jessy J's No. 1 smooth jazz single "Tropical Rain." He has received multiple Best Keyboardist nominations at the Oasis and National Smooth Jazz Awards.

Soul Secrets (2014, Nightowl) was his biggest radio success. By his biography's account "Elegant Nights" reached No. 1 in January 2015, "Rio Drive" was the most played song of 2015 on Alan Kepler's Smooth Jazz Top 20, and "Only You," written for his wife Yvonne, reached No. 2 in July 2016. After her death from brain cancer he stepped away from music for about four years, and he came back with Serenata (2021), his first solo piano album, built from original pieces and piano impressions of songs by Milton Nascimento, the Clube da Esquina circle and Caymmi. He served as musical director of the Dave Koz and Friends at Sea cruises from 2021 to 2023 and returned for the 2025 Iceland cruise, and his website lists 2026 dates that include a January run with Peter White at Jazz Alley in Seattle, Hammond organ trio shows in California and a September booking at Pizza Express in London.

Karukas is a melody-first keyboardist and one-man production unit: Discogs credits him with piano, electric piano, organ, synthesizers, bass and drum programming on his own albums, and he writes, arranges, records and mixes at his own studio. The result is the polished, groove-based sound of radio-era smooth jazz, with Rhodes and acoustic piano leads, brass and saxophone guests, and hooks built to be remembered. He came to that sound from Washington fusion bands, jingle work, R&B and pop sessions and television scoring, and he describes himself as a genre-crossing veteran of smooth jazz, Brazilian music, New Age and R&B-pop, so his catalogue sits closer to crossover than to straight-ahead jazz.

The strongest outside influence is Brazilian: Dori Caymmi and Ricardo Silveira are recurring collaborators from Sound of Emotion onward, and Serenata is built on Caymmi and Nascimento repertoire. Reviewers quoted on his website praise the album for its restraint, one calling it his truest heart after years of hit-making smooth jazz, another noting that he plays with nuance rather than pyrotechnics. English Wikipedia describes him as a smooth jazz pianist and lists David Benoit, Richard Elliot, Grant Geissman, Koz and Ronnie Laws among his Los Angeles collaborators. His Rippingtons years and the Omar Akram and David Lanz productions also tie him to the contemporary jazz and New Age sides of the same studio world.