Digital audio mixing in code?

Question

I'm writting code to crossfade 2 48Khz, 16 bit audio tracks. The code basically multiplies each sample by a given percentage and adds the results together. This works fine in most situations, however in some cases a "flutter" is heard (this is not present in either source). Any suggestions as to what causes this artifact?

The Count, thanks but not quite what I need. The site assumes all volumes are directly propotional, not one increasing and one decreasing, and doesn't address the flutter artifact or any for that matter.

Answer 1

Maybe this link will help you, I sure hope so :
http://oxygen.it.net.au/mixing/index.html