Can anyone explain:

1) Just exactly what is/was a "C Melody" sax, and why is it called that?

2) What's the deal with horns being tuned a half-step off what for other instruments is "concert pitch"? I had the opportunity to sing with an band featuring a horn section several years ago, and the leader who wrote the charts had an ongoing dialogue with the horn players about this discrepancy, while the horn players would occasionally make comments about how much easier things were for the less-musically-literate string players. Why would an "A" not be an "A" for every instrument?