Regarding instrumentation - Why 423.11?
I started writing brass arrangements while still in high school (late 70's) after first hearing the Philip Jones Brass Ensemble and Canadian Brass. Several years later, I had the amazing opportunity to write a bunch of stuff for the Denver Brass. The earliest charts were for 443.11. A few of those early arrangements were performed and recorded the next summer by the Summit Brass on their Toccata and Fugue recording.
A year later, the Denver Brass adopted as its standard instrumentation 423.02 (or 422.12) and as music director, I was called upon to write numerous charts for that instrumentation. This was a fabulous laboratory and I learned much about what (and what not) to do.
In 1993, we formed the Boulder Brass with a slightly different instrumentation (423.11 or 424.01) - a couple of our trombone players are also very good euphonium players and this opened up a new world to us. This instrumentation allowed us to explore the PJBE and London Brass library without compromise (and reinforce the horn part when necessary in those charts), and to also create a new library of charts.
There are well over 200 arrangements in our catalog now and those charts are being played all over by some of the worlds great brass players and ensembles.