RECORDING .INP RRPROnVClNG OF MUSIC ./A7> S/'lUiCfl 4Q7 



end to make the spiral coarser and in the case of the high end to run the 

 record at a higlier speed. Both of these changes tend to decrease the 

 time which a record of a given size can be made to phiy. The only alter- 

 native of these methods is to cut the record less loud than is the present 

 standard practise and make the reproducing equipment more sensitive. 

 This could easily be done if it were not for the "record noise" or "sur- 

 face noise," as it is conmionly called. Since this surface noise is already 

 loud enough in comparison with the reproduced music to be somewhat 

 objectionable, no appreciable gain in this direction can be made until 

 the technique of record manufacture has been distinctly improved. 



In this connection, there is one other interesting point. It has been 

 suggested that if electric reproduction were used, it would be possible 

 to cut the record with a characteristic other than uniform velocity sen- 

 sitiveness and correct for the error by an electrical system whose char- 

 acteristic is the inverse of the characteristic of record. If the change 

 which is made in the recording characteristic tends toward cutting at 

 uniform acceleration sensitiveness, the amplitude varies inversely as 

 the square of the frequency and hence the difficulties at the low end of 

 the scale are greatly enhanced. Similarly, if the records are cut more 

 nearly at constant amplitude, the radius of curvature of the sine waves 

 decreases as the square of the frequency, hence the difficulties are placed 

 at the upper end. In the process which is being described in this paper, 

 these limitations have been met commercially by having a frequency 

 characteristic of the uniform velocity type between the frequencies of 

 200 and approximately 4000 cycles per second. Below 200 it has been 

 necessary to operate at approximately constant amplitude with a re- 

 sulting loss in intensity which loss increases as the frequency decreases. 

 Above 4000 it has been necessary to operate at approximately constant 

 acceleration with its consequent slight loss in intensity at the very high 

 overtones. With a characteristic of this type, a range of frequencies 

 from 60 cycles to 6000 can be recorded with reasonable success although 

 the very low and very high range are slightly deficient. (See Fig. 14) 

 With a record having such a frequency characteristic, the inherent 

 limitations are divided between the two ends of the frequency band 

 and where electrical reproduction methods are used, it is possible to 

 employ a reproduction system whose frequency characteristic com- 

 pensates for that of the record. 



It should be pointed out that an attempt to record notes lower than 

 the low cutoff of the above mentioned apparatus would result in record- 

 ing only those harmonics of the notes which He above the cut-off. This 

 in no way prevents the listener from hearing the notes, reproduced by 

 means of the harmonics only, as notes with the pitches of the missing 



