Backus' acoustic research interests were evident from an early age. His senior thesis at Reed College was on the building of an electronic music generator, one of the first in existence. It involved the construction of a mechanical harmonic analyzer in the machine shop, and from then on he continued to build much of his own research equipment. He investigated the acoustics of both reed and brass instruments. His greatest contribution was to provide fundamental data on the nonlinear flow control properties of woodwind reeds. Also he greatly improved the capillary method for measuring the input impedance of air columns - a method widely exploited by many researchers. Backus devoted much time and effort to developing synthetic reeds for woodwind instruments, and he succeeded in producing clarinet reeds that were judged by reed experts to be of excellent quality.
His publications appeared in a broad spectrum of journals, ranging from The Physical Review to The Journal of Music Theory. He contributed twelve papers, plus numerous abstracts, letters, and reviews, to the Journal of the Acoustical Society of America. He is best known for his textbook, The Acoustical Foundations of Music (W.W.Norton, 1969), one of the first available texts on musical acoustics. John Backus died on 28 October 1988 in the UCLA Medical Center at the age of 77.
Shortly after the establishment of the Musical Acoustics Research Library at CCRMA, the John Backus Archive was created by combining files previously organized by CAS together with materials acquired from the Backus estate in Los Angeles. The John Backus Archive consists of published papers, correspondence, laboratory notebooks, book revision notes, and files with regard to his synthetic reeds. A fully searchable World Wide Web site has been created which details these contents.