Jim - Try this page. But it's also necessary to have good support and a relaxed throat. Sometimes when I'm learning a new song I am a little tense and find the upper notes uncomfortable. However, when I become more comfortable with the song and can relax more, the upper notes are fine. If not, I will experiment with different keys until I find just the right key for my vocal range. Sometimes that might be a differance of just a half tone. But then there's also the problem of finding an appropriate key for the accompanying instrument. For example, for my fiddle I find the key of E the hardest to play in - then I might go to Eb or F (I really like those 'flat keys' for the fiddle). Sometimes I find a song that really doesn't fit my vocal range - it's better for someone else to sing. Or I might change the melody slightly to avoid a certain high or low note.

Cheers, S. in Seattle