The term "Master Tape" gets thrown around a lot, sometimes with a notable lack of precision. This post is an attempt to clarify the several ways we use the term. It conforms to the common usages in the record industry. Perhaps you have noticed that The Tape Project is owned by two mastering engineers who have decades of experience in the record industry, so it should come as no surprise that we lean toward that standard usage.
First, let's go back before there was a record industry, and see how the word "Master" was used--not for people, but for things that people made. Paul Revere was known as a master silversmith, meaning that he made the original of each of the creations in his small factory, and journeyman silversmiths whom he had trained were tasked with making copies. The silver tea set that was sold to some prosperous Boston merchant embodied the artistry that had carefully beeen wrought into the master by Paul Revere. But the merchant took home a copy.
The fundamental meaning of the word "Master" is that it denotes something from which copies may be made. It does not inherently mean "Original Master" unless you put those two words together. As we will see there are legitimate cases of calling a tape a master when it is not an "Original Master."
In the age of analog pop recording it was common to do the initial recording on an analog multitrack tape recorder. For now let's say it had 16 or 24 tracks. Once the musicians, producer(s) and engineer(s) had finished recording the various elements of the song on the multitrack, it was "mixed down" through the console, and the output of the console was recorded to another analog tape, either single channel for a mono mix or two-channel for the stereo mix. The second tape embodied all the decisions the creative team had made regarding the balance of the instruments and voices, any tone adjustments they had made to those elements, and any sweetening or reverb or effects that they had added. If they liked what they heard when they played back that mono or stereo tape, then the tape was considered ready to move forward in the process of making records for the audience.
So which tape is the original master, the multitrack or the stereo tape? The multitrack came first, so should that be considered the original master? Maybe, maybe not, since it definitely does not meet the definition given above, that of being ready for making copies. How about the stereo tape? It is one tape generation later, so can it be called the original master? Yes, because it is the first tape that truly embodies the listening experience that the creative team has sculpted for the eventual listeners.
When I was coming up through the studio system of one of the major labels, we did not even call the multitrack tape a master, we called it a work part. But I haven't heard anyone use that term in a long time, so we just call it the multitrack tape. It's very commonly called a multitrack master, so if you call it that, everyone will know what you mean. But don't call it the original master.
Not all recordings start on a multitrack. For many years it was customary to make classical and jazz recordings right to a stereo or mono tape. Basically any music that was recorded all at once, rather than pieced together with parts added one after another, would be recorded straight to the stereo or mono tape. Parts from two or more performances might be edited together, and in the case of classical recordings commonly more than a hundred small pieces were put together to create a single performance. But it was all from the tapes that had been running as the musicians played, the first generation tape. When the various songs had been spliced in the correct order, you had a master tape ready to move to manufacturing. This describes a first generation tape, and it is also an original master.
To create Tape Project releases, we work from "original masters" (with one
exception.) Depending on how the particular album was made, it may be the mixdown tape, or the edited version of the original session tapes.
What about the other kinds of master tapes we hear about--the safety master, the production master, etc?
I was taught that a safety copy was as identical to the master as it could be made: same speed, same track layout, same level, same EQ. The idea was that if a portion of the master was damaged you could splice in a section from the safety master and the repair would be undetectable. We didn't call them safety masters, we called them safety copies, because their intended use wasn't for making further copies, they were held for repairs on master tapes.
Production masters served a different purpose, and they may or may not have been made as exact duplicates of the original master. In the days I'm talking about the release format was LP, later LP and cassette. (Let's not even talk about 8-tracks.) When we were cutting the lacquers for the pressing plants (also called lacquer masters, since they were destined to be the source of many copies once they got to the pressing plants) we sometimes made adjustments to the level of the various songs, tweaked the tonal balance, faded tracks out and so forth, as instructed by the producer, engineer and/or the artist. This process, called "mastering," was integral to achieving the artist's vision for their work. We commonly made tape copies as we were cutting the lacquers so we would have tape copies to send to the foreign affiliates, to send to the cassette plant etc, and these tape copies would reflect the same changes we made for the LP. (Contrary to audiophile lore, very few of these changes were made to get around the limitations of the LP format. Almost all of them were made to make the musical result closer to what the artist wanted.) The original master may have been quarter inch or half inch, 15 IPS or 30 IPS, IEC or NAB EQ, with or without noise reduction, as chosen by the creative team at the time they were making them. The production masters didn't necessarily duplicate those choices. Since they were destined for a production environment which may be on a different continent, the format was usually standardized with that in mind. A European label might be using the IEC curve in their studios, but make the production masters with the NAB curve to be shipped to the US. And vice versa. Production masters were commonly encoded with Dolby A noise reduction, even if the original master was not. It's legitimate to refer to these as masters, since they were designed for making copies, but it is inaccurate to call them "Original Masters." There are now a lot of these floating around in private hands, and they can sound pretty good. At least there's a fair chance that they were made directly from an original master.
There's another kind of production master you're less likely to encounter. In cutting lacquer masters for LP production, you have to execute all the changes you want to make in real time as you cut, and you have to do it correctly for a whole side at a time. If there are a lot of changes it can be a complicated dance for the mastering engineer. In some cases it can be impossible, such as an album that's compiled from many different sessions that might not have used the same speed for the tapes, or the same width, or the same choice of using noise reduction or not. In that case the mastering engineer will have to make a cutting master by copying the songs to a new tape one by one, incorporating all the necessary changes. For an interesting story about one such case see
story here.The tapes we use to create our albums, which we call running masters, fit the definition of a production master.
Also see:
What Is a Tape Project Album?What Is The Provenance Of Our Tapes? 
