TONALITY (from tonal, from tone, OF. ton, from Lat. foams, from Gk. rovoc, tone, sound, tension, strength, cord, from reiretv, teincin, Lat. tendere, Skt. tan, to stretch). In music, the grouping of certain chords around a central tonic chord. The principle rests upon the relationship which various chords bear to one another. Briefly stated, a tone is related in the first degree to all tones forming conso nant intervals with it; in the second degree to all tones forming dissonant intervals with it. Thus we can establish the relationship of D to C by means of the chord of the dominant seventh d-f,t-a-c, which is the dominant of G major, which, in turn, is the dominant of C major.
The relationship of single tones becomes in telligible only through the agency of chords. It is sufficient to recognize only two degrees. Since, when considering the relationship of chords, each chord is considered a tonic chord, it will perhaps be best to speak of triads. A sharp distinction must he made between similar and dissimilar triads: If a major triad is followed by another major, or a minor triad by another minor. the two major triads are similar; as are also the two minor triads. But if a major triad is followed by a minor, or vice versa, the two triads are dis similar. It must also be borne in mind that when speaking of major triads all intervals are reckoned upward; when speaking of minor triads all intervals are reckoned downward. A triad is related in the first degree to all similar triads whose fundamental tone is related in the first degree to the fundamental tone of the original triad. Thus the triad of C major is related in
the first degree to the similar major triads of (4, F, E, Ab, Eb. A. It is also related in the first degree to the dissimilar minor triads whose, fundamental lies a fifth below any of the tones of this C major triad. These are F, A, C, a fifth below C, E, G, respectively. To these must also be added the triad built upon the mediant, which in a major key is always a minor triad. Hence, every triad is related to ten other triads in the first degree. In the case of a minor triad similar relations exist. The triad of A minor is related to the similar minor triads of D, E, F, C; also to all dissimilar major triads whose funda mental tone is one of the component tones of the A minor triad, viz. A, C, E. To these is also added the triad of the mediant, which in a minor key is always a major triad.
All triads other than the ten just mentioned are related to the original triad in the second degree. Here the degree of affinity may be more or less remote. See Cumin; CONSONANCE; DIS SONANCE; KEY. For a full exposition of the sub ject, consult: H. Riemann. Musikalische Syntaxis (Leipzig, 1877) ; ,'?kizze ciner ncuen Methode der IIrrmonicleBre (ib., 1880) ; Systematise/lc Mo dulationslehrc 1887).