I'm a returnee to the flute world, this year I came back after a break of a couple of decades. I always played an Armstrong 90, and managed to do quite well with that, playing professionally and doing our Australian music exams up to Associate Diploma level. To celebrate resuming the faith, I indulged myself in a Muramatsu GX, which is giving a sweetness of tone I never ever got from my old Armstrong - that will surprise nobody! BUT, for the first time in a total of +/- 30 years of flute playing, I am finding intonation has become a major issue. When I check against the tuner which you can find on flutetunes.com, I'm finding the 3rd register is way sharp, and it's very hard to push it down (rolling the flute in to cover more of the aperture etc). And I'm finding that where, on my old flute, the finer tuning I did intuitively, now I hear it going out and really have to struggle to manage it. Yesterday I sat in with a local band playing some jazz, and in all the noise I couldn't hear myself very well. We were actually playing outdoors, under a tarpaulin, and there was very heavy rain bucketing down (typical band stuff, hey). I was tending to play in the higher range just to hear myself better, and it was at times so far out (in the wrong sense) that I wished I hadn't heard - totally embarrassing.
Apart from this I've been playing with a classical pianist friend in his music studio, in more or less ideal conditions. While in this set up I can at least hear the intonation drift when I start to get tired, and I can manage it better.
I'm finding this very frustrating - spend $$$$$ to upgrade and start to play out of tune ... What???? Do any of the experienced members of this forum have anything to say about intonation on better quality instruments?