Here's a late comment. This pic of Sinatra's system has been posted elsewhere, with numerous educated guesses as to its composition. It has been described by Shelley Herman many years ago who installed it. (google him and Sinatra to find it). The tape machine is a Presto 825, introduced in 1958, and Presto's only stereo unit. Used here as the AMPEX 440 series was not available. The Presto was available in 1,2,3 and 4 channel versions, for 1/4" (1 and 2) and 1/2" (3 and 4) tape. This permited him to play 3 track, 1/2" masters (vocals often recorded on the center channel). There was space for an additional 1/4 track playback head on 1/2 track machines, and it appears that in this photo he is playing a 1/4 track stereo tape, not a 3 channel 1/2" tape. One could change head blocks and guides between 1/4" and /2" tapes, but the changeover was not especially easy to carry out.