The Music IVB is a computer music software for sound synthesis. It was the first, among the Music N, to be developed outside of Bell Labs and research conducted by Max Mathews.
Background history – It was developed in 1963 by Hubert Howe, James K. Godfrey and Winham Randall (the latter was interested in using the computer for studies on the perception) at Princeton University. The reference software of Princeton was the Music IV of Bell Laboratories (Bell Labs). Max Mathews was to donate a copy with the source code.
The revision work – B is for BEFAP, the name of the assembler used by researchers at Princeton on their IBM 7094. It was a modified version of the FAP. The language used was the first problem with which the Princeton researchers had to do. In fact, the Music IV Bell Labs was developed with a modified assembly of their IBM 7094. This did not allow the use of the software on other machines of the same model. For this reason, with the collaboration of programmers Tobias Robinson and William Gale, it was necessary to rewrite all the code for new software.
News – The intention of the researchers was a desire to create software that was not just a updated version of Music IV, but a new program designed with the needs of users: the composers. The intention, therefore, was primarily to simplify as much as possible the approach to use. This, in intentions. In practice, however, the Music IVB does not make big news.
Limits – The greatest obstacle to all research at Princeton, was external to the software. The University did not have a DAC and this forced her to lean to the device at Bell Labs, almost two-hour drive. The situation improved only since 1965, when Bell Laboratories gave their 12-bit DAC at Princeton University. This would give new stimulus to both research and musical composition. Not only that: in 1963 it was not possible to exploit the potential that would offer the new generations of computers (such as the IBM 360, for example) that used integrated circuits technology, providing higher performance. All this led the Princeton researchers, in later years, to develop an updated version of Music IVB called Music IVBF. From this and from the same Music IVB, finally, comes also the Music 7, an updated version for the new computers at Queens College in New York.
For this topic I’ve read.
 James K. Randall, A Report from Princeton, Perspectives of New Music, Spring – Summer 1965, pp. 84 – 92.  Donald Mac Innis, Sound Synthesis by Computer: Musigol, a Program Written Entirely in Extend Algol, Perspectives of New Music, Fall - Winter 1968.  Hubert S. Howe, Music and Electronics: a Report, Perspectives of New Music, Spring – Summer 1966.  Jon Appleton, My Friend Max, Computer Music Journal, Vol. 33 , 2009.