I have a Getzen Eterna Flugle horn and found all noted played using the first valve alone are flat. I use a Monette FLG15. I switched out to a Bach 3c and found it wasn't as flat but still it was flat. I then we t to my favorite music store and tried a new Holten Flugle horn, the result was the same. Is it that I have to get use to agjusting my tongue every time I use the first valve? I don't find this issue with trumpet or Valve Trombone.