Sound is a vibration and can be used as a healing tool in meditation and can also be used to condition your mind body and soul in a way that only psychologists know. One way psychologists use this is through hypnotism, which meditation is a form of self hypnosis and can be more direct and in relationship to what you are working on.

Playing background music during meditation can help you relax and clear your mind. Having ambient music or guided meditation can help you with more specific areas, such as aligning or energizing your chakras. Sound can also be used to alter or condition your brain state and subconscious using certain frequencies, much like how hypnosis works.

The technologies such as Holosync(tm) or Brain Sync(tm) that use certain frequencies to alter brain states can be a useful tool for meditation. These technologies have been around since the 60's and have only recently become popular. There are many different forms and meditation for programming your mind and changing thoughts to positive thoughts, also for conditioning thought pattern's that will help you in your everyday life.

Ambient sounds can be useful putting you in a situation such as the beach with ocean waves or in a forest to take you away from the hustle and bustle of everyday living. Helping you to get to a relaxed state and listen to the waves crashing against the shore can take you to a happy place.

Guided meditations can help you follow instructions to achieve an outcome of well being or to strengthen your spirit. These are wide ranging and can be very helpful even when meditating, as they work at a sub-conscious level and can also be used during your normal sleep cycle.

The schumann frequencies have an effect on all objects, each chakra has its own frequency or note, for instance the heart chakra is a note at a certain frequency, this can be a useful tool when targeting specific chakra energy centers.

Here is a link to my friend's website. She creates binaural beat sound meditations for relaxation, healing etc.
Wonderfully soothing & calming. Very well priced her products are compared to other similar products which do the same thing but cost hundreds of dollars sometimes.

Unison Therapy - beyond meditation