This is mostly from memory - I don't have the score in front of me.

It's not an easy piece. Lots of timing things to work out with sections that usually sit across the room from each other, and harmonies that are only in one or two parts. It's very polyphonic/polyrhythmic, too - lots of things going on at once that don't line or match up with other parts. At times there are four or five lines occurring simultaneously.

You also have to have absolute boss low reed players - bassoon and bass clarinet especially. It's even better if you have a player who can also be on alto clarinet for the piece. That first sixteen measures sets the entire tone for the piece. Plus don't forget tuning octaves on the fifth and sixth partials in the brass, which happens a couple times in the piece.

It's achievable - but it very definitely earns its grade 4 and shouldn't be approached lightly.