How was the sound signal captured on phonograph records of the twentieth century?

a.The vinyl phonograph record has a long spiral groove on its surface. The grooves has a variable depth so the rotating record vibrate on different frequencies and amplitudes, corresponding to the original sound. Those tiny vibrations of the record are not seen by the eye or perceived by ear, but can be captured by the diaphragm and enhanced, making them perceivable to human ear.

b.The vinyl phonograph record carries the series of thin grooves, each of those grooves representing the numerical values of the the intensity and frequency of the sound in a short interval of time. The tighter those grooves are placed on the vynil, the closer the captured record sound to the original sound.

c.The vinyl phonograph record carries the series of thin grooves, each of those grooves representing the pure sine wave functions. Those sine waves are obtained by the Fourier analysis, and the greater the range of the frequencies of those functions of phonograph, the closer the musical output approximates the original sound.

d. The vinyl phonograph record has a long spiral groove on its surface. The groove has a variable depth, so the phonograph needle riding on the moving groove of the rotating record vibrates continuously at frequencies similar to the original sound. Those vibrations are then transferred to the diaphragm and enhanced.