Lou earned a Bachelor of Arts degree in music from Jersey City State College where he studied percussion with Nick Cerrato. He has also studied drums with Tony Inzalaco, Sam Ulano, and Beaver Harris, who became his mentor. In 1974, Lou was awarded a National Endowment of the Arts Fellowship for his studies with Harris. Lou also studied arranging and musicianship with Marshall Brown.
From the 1970s to the present, Lou has performed with a great variety of outstanding artists, including Borah Bergman, Eddie Bonnemere, Karen Borca, Rob Brown, Roy Campbell, Rio Clemente, The Copascetics, Dardanelle, Eddy Davis, L.D. Frazier, Yuko Fujiyama, James Garrison, Charles Gayle, Vinny Golia, Burton Greene, Urbie Green, Gunter Hampel, Johnny Hartman, Pucci Amanda Jhones, Phillip Johnston, Chris Jonas, Sheila Jordan, Janet Lawson, William Parker, Bu Pleasant, Perry Robinson, Roswell Rudd, Ken Simon, Paul Smoker, Steve Swell, Sol Yaged, Mark Whitecage, and many others.
The Reverend John Garcia Gensel, who Duke Ellington described as "the minister of the night flock," relied on Lou's versatility for more than a decade during the 1980s and early '90s as house drummer at New York's St. Peter's Church for many special events, including All Night Soul and Eubie Blake's 100th birthday celebration.
From the late 1970s until the early 1990s Lou was virtually absent from the avant-garde scene except for annual concerts with former Albert Ayler bassist Steve Tintweiss and two albums with vocalist Amy Scheffer. In 1984, Lou toured US military installations throughout Central America under the auspices of the Department of Defense. That year he also organized the Dixie Peppers, a sextet specializing in traditional Dixieland and Swing repertoire. Since 1980, Lou has led the Lou Grassi Quintet, featuring original arrangements of stylistically diverse music reflecting more than 60 years of the jazz tradition. In 1989, while playing Dixieland festivals and clubs throughout East Germany, West Germany, Switzerland, and Holland with the Warren Vache Sr. Syncopatin' Seven, Lou met the improvising keyboardist Andreas Böttcher in Dresden. Six months later, the Berlin Wall fell, clearing the way for a collaboration of the two that has produced two albums and annual tours of Germany since 1992.
In 1994, the Improvisor's Collective, a group of progressive New York-based musicians, was organized and enabled Lou to re-emerge fully into the avant-garde scene. Lou's 1995 concert for the collective was recorded and subsequently released as PoGressions (Cadence Jazz Records 1062), receiving critical accolades worldwide. This and subsequent recordings have firmly established Lou's place as one of the most versatile, original, and creative drummers working in this idiom.