I know that they discourage this in most orchestration books, but I know that it is done sometimes and I am looking for better practical guidelines. When is it okay to have an octave leap on the various instruments?
Piccolo? Flute? Clarinets? Oboe / English Horn? Bassoon? Trumpet? Trombone?
I am most often encountering two types of situation:
(1) In the reeds: Fairly rapid (16th notes at a lively tempo) alternation of a note and the same note an octave higher or lower.
(2) In the brass: a short phrase played in one octave and then repeated an octave above or below the original.