Programming a sound engine in DOS is no simple feat. Unless you are fairly adept at assembly or very good at C, I would not attempt it. But if you like self-inflicted pain you can check out www.creative.com
and go to their developer center. They have the old DOS manuals (legacy manuals) there which will tell you how to code for the older sound cards. Note that most modern cards do not support DOS at all so this information might not help. Also some of Creative's so-called backward compatibility with DOS does not always work very well. To program a DOS sound engine you should NOT be in a DOS session or you will get some very wacky results.