"Unlike 35mm which was first used in 1957, and dropped by most recording companies, this is the first time PROCESS 70 is being brought to the attention of the public. Process 70 is the development of a pre-emphasis characteristic which is less than that normally used. We can effectively increase the overload handling capacity of the electronics, as well as the tape itself while still maintaining as even wider bandwidth of reproduction. As the tape moves by the head faster an inherent increase in high frequency response results in its use. Process 70 takes advantage of the gain in the high frequency response to improve the transient gain in the high frequency boost and compensating for it by reducing the amount of the high frequency de-emphasis"The liner notes go in circles like that, very repetitive stuff. But it's basically describing a change in mastering. the end result to my ear is an album really short on bass response, but that's true of most everything before the late 1980s. Until the advent of all digital recordings everything was recorded on magnetic tape.
In this case "pre-emphasis" is a reference to a change in the magnitude of a band of frequencies, from the sound of the LP... very high ones. What they actually say is that in recording onto high speed tape, high frequencies are normally de-emphasized, to make it sound more normal. They do so to a lesser degree. I find the result shrill.
The engineer on the Billy May record I have here was Bill Putnam. In 1957 Bill founded United Western Recorders. It was a big deal independent studio in the 1950s and 1960s. In 1985 Putnam sold it to his partner Allen Sides, who renamed it Ocean Way Recording. Putnam was a big supporter of stereo sound. Bill stockpiled stereo recordings by orchestras as he handed over the mono mixes the labels ordered. Years later they came back to Putnam and paid up big time. Bill almost certainly had something to do with Process 70.