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One element of cost which had not much concerned the commercial studios was that of manufacturing the master records from which other records were made. The difference of $50.00 to $100.00 in the cost of making a master record meant little to a commercial organization which expected to turn out from 10,000 to 50,000 copies from this master record. It was realized from the beginning, however, that the demand for copies of a recorded book for the blind would probably not be much more than one hundred copies of any one title. Under such conditions, a difference of $50.00 in the cost of making the master record would mean a difference of 50cts on each disc. Accordingly, attention was first directed toward getting a maximum of reading matter on each disc at a minimum of cost. One way of increasing the number of words on a record was to have it revolve at a slower rate of speed. Various speeds were considered, but it seemed best to adopt a speed of 33 1/3 rpm, since motors for phonographs playing such records would soon be available on the general market because of the tentative interest which commercial concerns had already shown in recording at that speed.

The size of the records was important. Experiments were made with records thirteen and fourteen inches in diameter, but the twelve-inch record was selected for several reasons, principally because pressing dies for this size record were available, and a twelve-inch record seemed to be the largest which could be stored conveniently on shelves in common use. Later experience has shown that ten-inch discs are so much more conveniently handled than twelve-inch discs that the American Bible Society has re-recorded the entire Bible on ten-inch records. The Library of Congress has experimented to some extent with records of this size and found them popular. In the light of experience, economy would seem to be the only justification for making records over ten inches in diameter.

Further experiments showed that recording could be done on a record with grooves closer together than those generally used. A pitch of from ninety to one hundred grooves per inch was in common use. It was found that a good quality of recording for speech purposes could be obtained from records recorded at a pitch of from 150 to 200 per inch. Great care had to be taken, however, to record in such a way that the subject matter in one groove could not be heard while the adjacent grooves were being played. This faint sound coming from the adjacent grooves is known among recordists as echo, or is sometimes called "ghost." The higher the pitch (or number of grooves per inch), the greater becomes the difficulty of guarding against echo. The high pitch of recording reduces the material called "land" between the grooves. There is a tendency, therefore, for this land to break down causing repeating during reproduction.

All things considered it was decided that 150 grooves per inch was about the optimum pitch to be used. More recently, with the advent of lighter pick-up arms and greater skill of recording, it has been found possible to increase this pitch to 175 -- even to 200 or more -- grooves per inch. Experience may make it possible to increase the pitch to substantially over 200 grooves per inch.

It was decided to begin the recording on the outer edge of the record because blind people were more accustomed to playing ordinary phonograph records that way. In an effort to obtain as much satisfactory reading material as possible on a twelve-inch record it was found that when the needle was placed on the groove at the outside of the record a very satisfactory reproduction was obtained by lateral recording. This reproduction deteriorated as the needle approached the center. Down to an eight-inch diameter very good reproduction was obtained. From eight inches in, the quality rapidly fell off until, with the instruments available at a reasonable price in 1932, the quality at the four-inch diameter was reduced to the minimum acceptable for Talking Book records. This was due largely to the speed with which the sound groove passes under the needle. More recently, recording methods have been improved so that eventually books may sometime be recorded down to a three-inch circle. However, the space requirements of the braille label will always limit the size of the inner circle somewhat.

When the record revolves at 33 1/3 rpm the speed of the needle at the four-inch diameter is about seven inches per second. When the intelligibility of reproduction is the only thing to be considered, a needle passing through the groove at a greater speed is simply a waste of groove length. It had to be considered whether or not it was possible to produce a machine which would pass the record under the needle at seven inches per second from the time it was placed on the outer edge of the record until it reached the four-inch diameter. If the passage of the needle through the groove could be kept at a constant seven-inch speed it would require about thirty-three minutes for the needle to pass the full length of the approximately 2000 inches of groove of a twelve-inch record cut at a pitch of 150 grooves per inch.