But should Moscow audiences be expected to have heard of Birtwistle? (I ask objectively, not sarcastically or critically)
Yes, that was exactly my point. Should any audience be 'expected' to have heard of any other works than the ones they've come to hear?
I feel that Gauk believes (as I do) that it would be healthy for audiences to have listened widely to a variety of music from different nations and periods. But (again, objectively!) in reality it's not realistic to expect any significant or comprehensive knowledge of the output of composers of other countries in all listeners - people simply haven't the time, let alone the resources. Even getting hold of works by Birtwistle (or PMD, or James McMillan, or any other British cmpoosers of present or recent years) is a hard job that requires a lot of effort. There aren't CDs available of major works, nor can they always be found online. All you can find of The Mask of Orpheus is dribs and drabs, in disjointed chunks. Try finding Yan-Tan-Tethera (which I rate as a masterpiece)? Or The Second Mrs Kong? There's not a scrap of it to be heard. Frankly, composers (and their pubishers) have themselves to blame - while they sit tight on their output, passed-around on privately-made CDS in hardwritten paper sleeves, the world can rightly say... 'oh, and what have you written?'
I wish Sir Harry a happy 85th birthday, Perhaps his publishers would make him the birthday present of making available the recordings they're sitting on? Because if they are waiting to cash in financially on these works, they (and we0 will die waiting. Please don't tell me no-one bothered to record The Second Mrs Kong or Gawain, when they were performed?