Just turned 60 ....I only sing on recordings and am confident that I could not do it live because of nerves. I can get up to top E ish. What I have noticed however is that getting notes is all about relaxing and manipulating tiny muscles in the upper chest, throat, palate and behind nose area. There are tons of books on it. One good exercise to get the throat open is to drop the jaw, relax tongue and talk like boo boo (yogi bear). I am no expert but I think the high notes are a combination of getting the soft tissues in the palate to vibrate and push that sound into your head area.
On the other hand i may be talkin sh--e. I am sure there are good singers on BC who can give advice. It usually takes me a half hour of practice before I even get near relaxed. I play some tenor sax and use some of the breathing exercises to try and improve my singing voice. I don t think I could even consider playing and singin simultaneously.