In the early- to mid-1950s, Mancini was doing Universal horror films such as The Creature from the Black Lagoon. Many of these films had three composers working on a single film. After Peter Gunn, he generally ignored this phase of his career, although late in his life, he recorded some suites from these early scores.
Also, just before Peter Gunn, he did some LPs for Liberty, including the exotica album Driftwood and Dreams, later reissued as The Versatile Henry Mancini.
None of this music sounded anything like Peter Gunn or Breakfast at Tiffany's.