For those who aren't familiar with alto flutes, they are typically available with two types of headjoints:
Strait- Shaped just like a C flute headjoint, but larger.
Curved- Has a 180 degree bend in it. This type allows the player to play without reaching so far.
I originally purchased my alto with a strait headjoint. This was a demo model that was highly discounted. At the price I paid I could buy a separate curved headjoint if I found the I couldn't tolerate the long reach of the strait one. In the beginning I didn't play it for extended periods of time, but recently had more opportunities to play more often.
Now that I'm practicing and playing for longer sessions, I'm finding that when I reach for the keys for the right hand, the angle I need to hold my hand in is quite uncomfortable. Not only does it cause tension in my hand, but I also found that my technique wasn't very good in the right hand. My pinkie seemed to have a mind of it's own! What I didn't realize when I started playing alto, was that much of the music written for it utilizes those really low notes that require a lot of right pinkie dexterity.
So I bit the bullet. I had a curved alto headjoint sent to me on trial, and before the trial was over I decided I need to switch. The tone quality is very similar between the two headjoints. I can get a variety of timbres and colors from both of them. They were both made by the same manufacturer, however they were made of different materials, and the curved one I tried was marketed as a more entry level model.
The comfort level. however is like night and day! It took a little experimenting to find the perfect position for the headjoint. It doesn't go behind the body as one would expect. It actually should be up above the body and only slightly back. For me it was slightly higher than 45 degrees. The flute felt very stable once I found this sweet spot and I noticed an immediate improvement in my technique. This is of course due to releasing all that tension in my hands. It was also very balanced so there wasn't any "wiggling" as I changed notes.
There are of course trade offs to having a curved headjoint. The intonation is a bit wonky in the sense that the upper and lower registers are not well in tune with each other. The 3rd octave is quite sharp. There are alternate fingerings that can help, and that will take a little learning. If you play on one, you may find that you need to tune differently for different pieces depending on how much of the piece is played in the higher register.
I think the extra mental work is worth it however. There's no good reason to tolerate pain when you play. Not only does it discourage you from practicing (because it's no fun!) but its also dangerous. Repetitive motion injuries should be a major concern for instrumentalists. If you want to play for years to come, you need to take care of yourself.