Loudness and pitch are psychological terms which are used to describe sensations produced when certain types of waves operate upon the hearing mechanism. Intensity and frequency are the corresponding terms to describe the physical quantities power transferred per unit area and vibrations per second executed by the sound wave. The relation between these psychological and physical aspects of a musical tone has been investigated using a group of typical listeners. Precise scales were invented and used for representing the sensations of loudness and pitch. In comparing loudness a pure tone having a frequency of 1000 cycles per second and with intensity variable throughout the audible range is used as a reference tone. In comparing pitch, a pure tone having a constant loudness and with frequency variable throughout the audible range is used as a reference tone. The intensity of a complex tone with ten components all equal in intensity but different in frequency is ten times that of each component, as is well known. On the other hand, the loudness of one such complex tone with frequencies which are harmonics of 500 cycles per second was found to be equal to that of the 1000 cycle component raised one thousand times rather than ten times in intensity. An observer's location of the pitch was found to depend upon the intensity as well as the frequency. For example, the pitch of a 200 cycle tone was located at a position which was as much as one-quarter of an octave lower at the very high intensities than at the low intensities. For pure tones having frequencies near 2000 or 3000 cycles per second, no difference of pitch was observed as the intensity was changed. Similar small pitch changes were observed with complex tones. Some very large changes were observed with particular changes in the components. For example, the pitch of a complex tone having four components of equal intensity, but with frequencies of 400, 600, 800, and 1000 cycles per second, was perceived as that corresponding to a 200 cycle tone. If to this complex tone, three additional components having frequencies of 500, 700 and 900 cycles per second, are added, then the pitch will be perceived as an octave lower or that corresponding to a 100 cycle tone. An experimental demonstration will be given.