Miller Puckette was the original developer of Max at IRCAM, Paris in the 1980s.
Max was subsequently augmented with real-time signal processing (FTS - “faster than sound”) in the late 1980s, which ran on NeXT computers with ISPW boards.
A commercial version of Max for Macintosh computers was released by Opcode Systems, Inc. in 1990 under the lead of David Zicarelli.
Miller Puckette moved to UCSD in the mid-1990s and developed an open-source version of Max/FTS called Pd.
Opcode stopped supporting Max in the mid-1990s. David Zicarelli acquired Max in the late 1990s and sold it through Cycling '74.
Audio processing objects from Pd were incorporated into Max/MSP around 2000.
Pd contains about 180 objects, but another 300 or so externals are available online.