Consumer popular audio today consists mainly of music in the form of CD's, MP3, Radio (AM, FM, satellite), Minidisc, and DVD's. Players and recorders are more mobile and personal than ever before. 

Music used to be delivered over the radio and could be recorded on a home tape recorder or sold in stores on record albums for play on home turntables connected to stereo amplifiers and heard thru two speakers. Overall the sound was not bad except for the background hiss produced by tapes and the constant radio commercials. Record albums allowed the listener to skip the commercials at a small cost of course. 

Digital music such as on a CD, eliminates most of the objections in sound quality of decades ago. The addition of surround sound, using multiple channels instead of just two, adds to the overall enhanced listening experience. In addition, the ability to record your own music, song by song, picking and choosing the exact tracks you want, customizes and fine tunes the listeners personal preferences along with the digital compression of music, thereby allowing you to literally carry your entire music library in your pocket.

MP3 players today can store thousands of songs. You can download songs from the internet for 99 cents each, about the same cost as buying a CD which typically contains 10 to 20 tracks and costs around 15 dollars. The advantage of the internet approach is you do not have to buy all the songs on a CD to get the ones you want, thereby saving a few dollars potentially on every CD that you would have purchased.

What is surround sound?

Surround sound (also known as multichannel sound) incorporates multiple speakers to envelop the listener, providing sound in front, to the sides, and behind. Movie theaters use surround sound to impact large audiences with the feeling of being in the middle of the action. Surround sound is an essential element in creating the home theater experience.

Dolby Surround Sound

Dolby Surround Sound is the earliest form of surround sound. It is a three-channel process meant to recreate a theater experience. The Dolby stereo track is channeled into the front left and front right speakers. A mono signal is then fed into both rear speakers.

Dolby Pro Logic Surround Sound

Dolby Pro Logic is an advanced version of Dolby Surround Sound, adding a center channel speaker for music and effects. It is a four-channel system that directs the information to certain speakers. The four channels are the set of front speakers, one center channel speaker and one rear speaker.

Dolby Digital (AC-3) Surround Sound

Multichannel format introduced in 1996 presents 6 discrete audio channels. (Also described as 5.1) 5 of the 6 channels carry the entire bandwidth of sound with the 6th speaker or LFE (Low Frequency Effects) Channel carries all the low-bass sounds. This enables you to maximize your action-adventure sequences with fuller explosions and sound effects. You are still able to hear bass sounds from your left and right front speakers even without a subwoofer, but you won't experience the full impact of audio without a subwoofer.

DTS Digital Surround

DTS Digital surround sound and Dolby Digital surround sound are nearly the same. The basic difference between these two formats is the method of compression or how the large audio data files are manipulated to fit in less space. In theory, this means more overall information available on the soundtrack. These two formats are not compatible, and require their own branded decoding chips on AV receivers and processors, as well as separate digital outputs on DVD players. DTS and Dolby Digital will continue to co-exist in the marketplace.

THX

THX is a set of technical specifications in order to standardize the performance of surround sound. George Lucas developed these standards shortly after the film "Star Wars" was created. He did so in order to standardize the audio and video experience in theaters across the world so that his films would be represented as they were made, essential trying to recreate the original.

Manufacturers of all theater and A/V products have been giving a set of performance specs that their products must to meet in order to meet the THX certification. 

THX is a certification that can be an indication of how well a product has been built - although it should not be the only indication. Some manufacturers choose not to participate in the program preferring to build product to their own specs.