Alfred Publishing.
The American educational publishing standard since 1922. Alfred publishes more piano method books than anyone except Faber, the Premier Piano Course, the Belwin Mills band catalogue, the Sing & Play series, and the Belwin classical critical editions. Plus the official sheet music for hundreds of pop and movie standards.
Alfred Music — founded in 1922 by Sam Manus and named for the Sam Goody owner Alfred Haase — is the second-largest educational music publisher in the United States. The Alfred's Basic Piano Course (and the related Premier Piano Course) is one of the two most-adopted piano methods in American studios. Belwin Mills (acquired 2005) carries the school band and orchestra educational tradition, plus the Belwin classical critical editions used by orchestras and conservatories.
Below: the Alfred departmental catalogue. Method-first for the major piano, band and string method series, then format for the popular folio, theatre, film and Disney sub-libraries.