SACDs (Super Audio Compact Disc) are recorded at a much high sampling rate than normal digital audio (64x higher, I believe.) The resulting sound is much fuller and warmer than standard digital audio when played back on an SACD player. Most SACD recordings, this one included, are dual layer or "hybrid" so they will play on either type of player. Sadly, they seem to be losing favor among the major record companies, which is a true shame in light of the vastly improved sound.