Try burning at 'minimum' speed the disk allows (eg: instead of 50 speed, choose 16 or 20 speed). Also use decent brand CD-R's, not those made in Taiwan or China. The slower speed CD-R disks are also 'more reliable' than the high speed ones & likewise burn those at minimum speed (eg: 16 speed disk, burn at 4 speed). Sure burning fast is convenient for data back up, but for multimedia such as video or audio, slowest is always best.
Give your burner a clean too. They do get dirty I assure you. I use regular CD player cleaner disks to clean the laser heads.

Another option is to convert your audio files to WAV or AIF first, then burn them as an audio CD. But it also depends on how your burner program works.