The American Society of Professional Audio Recording Services has come up with a three-letter code which is printed on many CD/DVD discs or their covers and denotes the quality or recording. The codes and their menaing is as follows:
DDD: Digital tape recorder (or digital medium) used during session recording, mixing and/or editing and mastering (transcription).
ADD: Analog tape recorder used during session recording, digital tape recorder (or digital medium) used during subsequent mixing and/or editing and mastering (transcription).
AAD: Analog tape recorder used during session recording and subsequent mixing and/or editing; digital tape recorder (or digital medium) used during mastering (transcription).
Nowadays, this may be entirely meaningless as studios may convert the original digital signal (music) to analog and then to digital more than once during mixing and editing. Therefore, although the disc may still bear the DDD code, the full digital sound processing is not absolutely true. Thus, take into account the three-letter sound quality code as just an indication of whether the recording was first made on a magnetic tape (AAD or ADD) or on a digital medium (DDD).
In some cases labels have come up with their own sound quality indications, such as 4D or 24 bit/96 kHz. As a lot of other factors play a significant role in the final acoustic result, these indications may not be used as the sole reason for buying CDs. The same holds true for DVD-Audio, Dolby Digital and DTS indications on DVDs
MP3 is a compressed (lossy) audio file format used with portable audio devices and computers. Lossy compression means that some of the music information is depressed in such a way so that the music piece will sound close to a music CD. However, by definition (lossy) the sound is of inferior quality compared to the original recorded music.
MP3 files come with different bit rates all the way to 320 kbit/s (kilobits per second). The higher the number the better the quality. However, an MP3 sound even at the highest bitrate of 320 kbit/s compared to a 1411.2 kbit/s of CD digital audio format is definitely of inferior quality.
On the other hand, MP3 files can be loaded on a portable audio device and listend to on the road.
A number of labels are offering an extensive selection of classical music MP3 files for downloading. Depending on your music system, the sound may be from fine to unbearable. You make the final decision on whether to invest on MP3 files insetad of CDs!
SACD and DVD-Audio or DVD-A are higher fidelity audio CD and DVD formats that have not been a success so far as they requirw a home theater installation in order to unleash theur full musicality. Despite their superior sound quality there are generally few releases on SACD or DVD-A.
A large number of recitals and opera performances are made available on DVD and on Blue-Ray discs (high definition=better picture). The great majority are old TV or Video-cassette releases that have been transferred to DVD sometimes without any image improvement. They are available on the old 4:3 screen aspect ratio and may have digital sound improvements. New productions use the modern high definition 16:9 screen aspect ratio to match the modern widescrean TV sets. The sound as well as the picture is digitally recorded at high definition (a lot higher than the normal TV standard). Once more, what matters is the performance preferabbly accompanied by a descent sound rather than the higher quality of the picture.
Don't be confused with dolby digital and DTS or any other digital surround sound format as they usually make no difference to a classical music listenet/viewer.