in general, something that serves as a base or foundation for another.

Music. A fundamental sound is that which forms the lowest note of the chord, and from which are deduced the harmonical relations of the rest; or which serves for a key to the tone. The fundamental bass is that which serves for a foundation to the harmony. A fundamental chord is that whose base is fundamental, and in which the sounds are ranged in the same order as when they are generated, according to the experiment so often repeated by M. d'Alembert in his Preliminary Discourse and Elements of Music. As this order removes the parts to an extreme distance one from the other, they must be approximated by combinations or inversions; but if the bass remains the same, the chord does not for this reason cease to bear the name of fundamental. Such an example is this chord, ut mi sol, included in the interval of a fifth: whereas, in the order of its generation, ut sol mi, it includes a tenth, and even a seventeenth; since the fundamental ut is not the fifth of sol, but the octave of that fifth.

FUNDAMENTAL Bass. This part in music is, according to Rousseau, and indeed according to all authors who have proceeded upon M. Rameau's experiment, in its primary idea, that bass which is formed by the fundamental notes of every perfect chord that constitutes the harmony of the piece; so that under each chord it causes to be heard, or understood, the fundamental sound of that particular chord; that is to say, the sound from whence it is derived by the rules of harmony. From which we may see that the fundamental bass can have no other contexture than that of a regular and fundamental succession, without which the procedure of the upper parts would be illegitimate.

To understand this well, it is necessary to be known, that, according to the system of Rameau, which Rousseau has followed in his Dictionary, every chord, although composed of several sounds, can only have one which is its fundamental, viz. that which produces this chord, and which is its bass according to the direct and natural order. Now, the bass which prevails under all the other parts does not always express the fundamental sounds of the chords; for amongst all the sounds which form a chord, the composer is at liberty to transfer to the bass that which he thinks preferable; regard being had to the procedure of that bass, to the beauty of the melody, and, above all, to the expression. In this case, the real fundamental sound, instead of retaining its natural station, which is in the bass, will either be transferred to some of the other parts, or perhaps even entirely suppressed, and such a chord is called an inverted chord. For farther particulars relative to this subject, see Music.