Originating in Pittsburgh, Pennsylvania, Marmarosa became a professional musician in his mid-teens, and toured with several major big bands, including those led by Tommy Dorsey, Gene Krupa, and Artie Shaw into the mid-1940s.

His mental stability was probably affected by being beaten into a coma when in his teens, by a short-lived marriage followed by permanent separation from his children, and by a traumatic period in the army.

[3] He received the uncomplimentary nickname "Dodo" as a child because of his large head, short body, and bird-like nose.

[5][9] He was first mentioned in the national jazz press the following year, appearing in Down Beat magazine for his playing at a jam session.

"[10] After Krupa's orchestra broke up in the middle of 1943, Marmarosa played in Ted Fio Rito's band for at least a month that summer.

[10] From April to October of that year he was with Tommy Dorsey, including for the orchestra's appearance in the MGM film Thrill of a Romance.

[5] From the early 1940s Marmarosa had searched for and experimented with advanced progressive forms of jazz,[2][5] and had become increasingly attracted to bebop after meeting and jamming with the leaders of that new movement, Dizzy Gillespie and Charlie Parker.

[5] Leaders of these sessions included Wardell Gray, Lionel Hampton, Mel Tormé, Willie Smith, Lester Young, and, with Marmarosa as house pianist for Atomic Records, Slim Gaillard and Barney Kessel.

[5] With a few exceptions, however, Marmarosa only rarely played in public with the leaders whose studio recordings he appeared on during his time on the West Coast.

[5] Between the frequent recording sessions, he played "in big bands (especially Boyd Raeburn and Tommy Pederson), at jazz concerts, as a soloist in nightclubs [...] or jamming after hours.

"[5] Raeburn's orchestra was a progressive group that used "modern arrangements seeking to bridge the gap between bop and advanced European music".

[15] Marmarosa made his first recordings as leader in 1946, with trio tracks that included Ray Brown on bass and Jackie Mills on drums, and in a quartet with saxophonist Lucky Thompson added.

[17] In the same year, he featured in some of Gene Norman's Just Jazz concerts,[5] and was given Esquire magazine's New Star (piano) award.

[1][5] Shaw and DeFranco raised the idea of psychiatric treatment, but the former was rebuffed by Marmarosa himself, and the latter by the pianist's parents: "They were not reconciled to his needing professional help.

[5] His ex-wife remarried and asked him to allow her to change the children's names in exchange for not having to pay her any more money; following the advice of his parents, he signed the documents.

[5] This exacerbated his problems: several months in a Veteran Administration hospital preceded his discharge,[20] at which point he was in a poor psychological condition.

[5] Back in Pittsburgh, where he played locally from March 1956,[5] Marmarosa continued to be erratic, sometimes disappearing for weeks at a time, and giving his money away: "It was like he was on the road to self-destruction", commented trumpeter Danny Conn.[20] Amateur recordings from the pianist's concerts in Pittsburgh in 1958 were released four decades later by Uptown Records.

[20] One album from these, Jug & Dodo, contained trio and quartet tracks, with saxophonist Gene Ammons; it was released on Prestige Records more than a decade later.

[6] For the rest of his life, Marmarosa alternated between living with his sister Doris' family and in a veterans' hospital, both in the Pittsburgh area.

[6] Irritated by telephone calls from a fan seeking an interview in 1992, Marmarosa passed on the news that he had died; this led to premature obituaries being published in two British newspapers.

[5] Jazz critic Marc Myers, in comparing Marmarosa with other pianists of the early bebop period, observed that he was less aggressive than Bud Powell, and more expressive and complex than Al Haig, and that he "had a punctuating, full-keyboard approach, developing ideas in the middle and widening out to express them.

"[26] Critic and musician Brian Priestley wrote that "What was so distinctive about Dodo's work was partly his harmonic sense and knowledge of the additional notes [...in bebop.]

[20][27] Biographers commented that "his even, classically derived articulation had given way to a more rhythmically pronounced, jazz-oriented playing, and, above all, his musical personality seemed still more determined and coherent.