Ok, I would say it's pretty safe to assume that your using your oboe embouchre right now on the tenor? On oboe, or clarinet, or anything like that, your bottom lip is going to be stiff as a board if you're doing it right. On sax, it's basically the opposite. Especially for jazz, you're going to want to make an O shaped embouchre. More advanced jazz players often will have their bottom lip all the way out. First, just try a basic O shape, and you'll find yourself having a lot more control, and a more open tone. If you keep your bottom lip stiff and tight on sax, you just cut off the vibrations of your reed, get a stuffy sound, and have almost no control. Also for a more open tone, don't close up the inside of your mouth. Keep it open, as well as your throat. For jazz, you should really never use anything bigger than a 3, unless you're a freak like Bird and use a 5. For jazz, to start off with, buy something basic. Try either an Otto Link Tone Edge 6*, or a Meyer 6M. Again, these are very basic jazz pieces, and are great for getting your tone together. Either one will last you a year or two. Mostly, just relax when you play. An oboe is such a tense instrument, when you play the tenor sax, you just have to be in a whole different world.