How come the valve-trombone is not used in a orchestra ?

The valve trombone has a reputation among musicians for having an inferior sound quality. Brelioz, while appreciating the valve trombone’s ability to negotiate rapid passages, remarked that it had less “correctness of intonation”. It enjoyed a period of popularity in the 19th century, but von Gontershausen wrote in 1855 that the best German players were trading in their valved instruments for the good old slide trombone.

For a fascinating look at some of the design permutations the trombone has gone through, Look here

harp: very interesting.

Three questions about swinging and then one about the valve-trombone.

Ok.