Disjunct
Melody that moves by leaps.
What it means
Disjunct describes a melodic movement that proceeds in leaps — that is, in intervals larger than a second. The counterpart is conjunct movement in steps of a second. Most melodies combine both: stepwise movement carries the coherence, leaps give contour and breadth.
In addition, the term has a second, older meaning: in the doctrine of building the scale from tetrachords, two four-note groups are called disjunct if they are separated by a whole tone, and conjunct if they share one note.
Musical use
The mixture decides the character of a line. Vocal music, especially of older character, prefers stepwise movement, because it is singable and easy to hit; leaps appear there usually as thirds or fourths and are often balanced by contrary motion — after a large leap the line leads back in the opposite direction. Instrumental music is freer in this: themes based on broken triads are disjunct throughout and owe their pregnancy precisely to the leaps. In the study of composition the rule holds that leaps want to be prepared and caught, so that the line remains singable.
For the ear the difference has consequences: stepwise movement is heard as a coherent line, leaping movement rather as the outline of a chord. Large leaps can also create the impression of two separate lines if they alternate regularly between two registers.
Disjunct melody is typical of instrumental music, because instruments execute large leaps more easily than voices; fanfares, too, move in broken triads for this reason. In vocal polyphony, by contrast, a predominantly stepwise voice-leading was the ideal. Large leaps have a strongly expressive effect and are often used to emphasize particular passages of text.
Performance practice
Practise leaps as an interval, not as two individual notes: grasp the distance in the notation and play it as a movement. Sing a theme before you play it — what can be sung is also easier at the instrument. And watch the continuation after a large leap; where the line leads back, the peak note need not be additionally emphasized.