He is best known as the co-lead vocalist, guitar and keyboard/synthesizer player for the long-running band Blue Öyster Cult, with work on more than 20 albums.

One day in late 1968 some members of the band Soft White Underbelly, Donald Roeser (later Buck Dharma), Allen Lanier and Andrew Winters, entered the store.

In 1976, their platinum album Agents of Fortune with its hit "(Don't Fear) the Reaper" launched the band into international fame, though that particular song was sung and written by lead guitarist Buck Dharma.

Both Creem readers[5] and Rolling Stone critics[6] voted "Don't Fear the Reaper" as the top single of the year.

"Black Blade" was written from the point of view of Moorcock's Elric character, and the other two were "The Great Sun Jester" and "Veteran of the Psychic Wars", the latter of which was used in the original Heavy Metal movie.

In 2006, Bloom began a partnership with artist Philippe Renaudin, to create and sell six elaborately painted custom-made guitars, each one of which interprets a different Blue Öyster Cult song, and each of which was played during BÖC performances.