The aim of this article is to assess the relative merits of two approaches to teaching musical improvisation: a music-theoretical approach, focusing on chords and scales, and a "dramaturgical" one, emphasizing questions of balance, variation and tension. Adult students of music pedagogy, with limited previous experience in improvisation, took part in an improvisation course during which they were given either music-theoretical or dramaturgically oriented instruction. The students' melodic improvisations over a chordal accompaniment from the beginning and the end of the course were subjected to evaluation by a panel of expert judges. The music-theoretical instructions led to a more significant change towards improvisation judged as "dissonant" and "independent of the chord changes", whereas dramaturgical instructions led to a more significant change towards "rhythmically varied" playing.These and other results from the expert judgments are compared to the improvisers' self-evaluations as well as computational analyses of rhythmic entropy in the improvisations. (Contains 2 notes, 3 tables, and 1 figure.)