Which concept refers specifically to the repetition of a musical idea transposed up or down in pitch?

The concept that refers specifically to the repetition of a musical idea transposed up or down in pitch is known as a sequence. In music, a sequence takes a given melodic phrase and repeats it starting on a different note, effectively maintaining the same interval relationships but altering the pitch. This technique is commonly used to build tension and development in a piece of music.

For instance, if a melody begins on C and is repeated starting on D while maintaining the same contour and intervals, this is a sequence. Sequences can be ascending or descending, and they contribute to the harmonic and melodic structure of a composition.

The other terms, while related to repetition in music, describe different concepts. Repetition refers to a direct duplicate of a musical idea without transposition. Pedal point involves holding a single tone while harmonies change around it, and ostinato is a repeating musical phrase or rhythm throughout a composition. Each of these serves a unique purpose in music but does not imply transposing a melodic idea as a sequence does.