Yeah, you were probably out of tune then. The worst sound comes from two notes that are very close, like if you played a G and he played a F# (out of tune). Than that would sound pretty horrible. :)

As for a sound that vibrates at 440 vibrations per second always written as A. I have to disagree. If your talking about a sound that vibrates at 440 vibrations per second being known as the sound of A. That's right. Maybe it's how you stated it, but if a Eb Baritone Sax played a B note. Than that note would be D on the guitar. 440 vibrations per second is known as concert pitch (concert A). Some instruments aren't in concert pitch though, they are written in different keys. Like if you wrote a guitar part in C major, you would have to write the Sax part in Eb major. It's a stupid rule but hey it's worked for centuries. :confused: