Conjunct
A melody moving in steps of a second.
What it means
Conjunct describes a melodic movement that proceeds in steps of a second, that is, stepwise from neighbouring note to neighbouring note. The counterpart is disjunct movement in leaps. In addition there is the older use in the theory of tetrachords: two four-note groups are called conjunct if they share one note, and disjunct if a whole tone separates them.
Musical use
Stepwise movement is the basis of the singable melody. It is easy to hit, connects the notes into a coherent line, and carries the melodic flow; leaps, by contrast, give contour but tire when they get the upper hand. Most successful melodies combine both, with stepwise movement predominating and leaps standing at striking places.
In the study of composition, stepwise leading counts as the normal thing, from which departures want to be justified: after a larger leap the line should lead back in the opposite direction, and dissonances are resolved stepwise — suspension, passing note, and neighbour note are all stepwise formations. For the connection of chords too, the rule holds that every voice should take the shortest path; from this a largely conjunct course of the inner voices results.
The bass behaves differently: it leaps more often, because it carries the roots of the harmonies. Precisely for this reason a stepwise-led bass has a special effect — for instance in the descending bass figure of the lament.
Conjunct melodies are easily singable and count as the ideal in vocal polyphony. Gregorian chant moves predominantly stepwise. In melodic theory it is often recommended to let a larger leap be followed by stepwise movement in the opposite direction so that the line stays balanced.
Performance practice
Lead stepwise lines as a coherent movement with a goal, not as a sequence of individual notes — this succeeds best if you sing them first. Take care that no note falls out of the line: evenness in sound and length matters more here than emphasis. And use stepwise movement for memorizing; it is easier to retain than sequences of leaps.