How does the clarinet actually sound in a particular given octave range? Is this part going to be too low for the oboe? How can my cello part here best accompany that awesome sweeping violin theme tune I’ve just written? And when do I bring in the french horns - how will that alter the overall ‘feel’ of the piece at this particular moment?
A full woodwind and brass section right there, waiting to do your bidding! So how do you create your musical ideas in such a way so that each part sounds perfectly tailor made and ‘just right’ for that instrument? Imagine having a 60-piece string orchestra just sitting in front of you, ready to play your latest composition.
Some composers still enjoy the amazing privilege of working with a live orchestra to record their work.