After 2 years of playing, I thought my main problem was not hitting high notes and certainly not altissimo. All of a sudden I started squealing (almost always a very high D) whenever I reach for a high note. This has never happened before! I am using a Meyer 6 and La Voz mediums. I tried higher strength reeds (Vandoren 3 and even 3-1/2) to no avail. Out of desperation I pulled out a Rico Royal 2 and...no more squealing. Of course now the F and F# are even harder to play so I can't win. I did a search and followed the recommendations by @jbtsax to check the instrument. (using just the tone producer and checking for pitch, etc.) and the sax seems fine. Any suggestions would be appreciated and thank you!