If you're asked to
sing a given interval then I can see it *might* be useful, but it's surely just
as easy/quick to run through a scale in your head
Yes it's just as easy to do that but that doesn't achieve anything. This is a means to an end - the ability to recognise a given interval and, if necessary, reproduce it.
My horn pupils need to be able to recognise an interval and know exactly what it sounds like - if they can't do that then pitching is that much more difficult. There isn't time to run up a scale to work out the interval and the note to which they are rising could well be one of 4 or more which are playable with the same fingering so they have to know what it sounds like if pitching is to be anything more than pot luck.
All the best,
Lawrence
http://lawrenceyates.co.uk
