Mr. Gilman gave his second lecture on Music in Sever 11 last evening. Following is his abstract
In the first lecture we defined a note as a single sound having distinct pitch. It has long been known that in some notes such as those of the voice and stringed instruments, what we call the pitch of the note is accompanied by a number of higher and fainter pitches. These are called overtones. The researches of Helmboltz have proved that this is not the exceptional but the common case and that comparatively few instruments (the tuning fork being one) give notes in which the pitch we principally notice is the only one apparent to closer scrutiny. According to his theory timbre, or the characteristic quality which differentiates notes of the same pitch from different sources depends upon whether or no they are composite; and if composite, upon the nature of the group of overtones that therein attend the fundamental pitch. The physical cause of the composite nature of the notes of most instruments is the tendency of elastic bodies to vibrate in a way capable of analysis into a number of manners of vibration having different rates. In some sources of tone the quicker of these vibrations are always an integral number of times as fast as the slowest, (which is also generally the strongest). In others the quicker rates are in general fractional multiples of the slowest. To the latter class belong instruments like bells and drums giving less perfect notes; the former class including all musical instruments properly so called. The cause of this aesthetic distinction Helmboltz found in the fact that in notes with fractional overtones there is always interference between the various pitches constituting the total mass of sound, while in notes of the integral class this does not occur except when very high overtones are present. They are absent in flute notes, those of the piano and sweet voices; their presence gives their sharp quality to string and reed instruments and their crashing timbre to instruments of brass. The next lecture will suggest that some supplementary considerations are needed fully to explain the aesthetic differences in notes.