When I meditate inside our home rather than outdoors, I often find mantras to be helpful whether chanting or singing, whether listening or vocalizing myself or both. They provide a point of focus that allow my busy, 'monkey-mind' to rest.
One of my favorite CD's to listen to during meditation, if I want mantra rather than solely instrumental, is by On Wings of Song & Robert Gass called Heart of Perfect Wisdom which consists of both the longer (30 minutes) Gate Gate and the short (12 minutes) Beyond The Beyond. Both of these are incredible for assisting induction into deep meditation, although especially the shorter piece so it can be nice to start with that one even if we wish to continue moving into a longer meditation.
I bought this CD in 1995 and it has been a valuable musical aid over the years when I feel the need to center but am unable to go out into nature and/or simply want to go within wherever I am. The Tibetan Bells, Singing Bowls, and very low, Tibetan style chanting result in sonic entrainment -- they produce extremely low frequencies which actually entrain the biological rhythms of the body and help induce the brain waves, heart beat and respiration of the listener to resonate to these frequencies. ... [and the high frequencies] seem to charge and energize the cortex of the brain. (Jonathan S. Goldman, Director, Sound Healers Association)
Sound and mantra (chanting) in meditation is referred to by everyone from Jon Kabat-Zinn (Director of Center for Mindfulness, UMass Medical School) to David Frawley (Ayurvedic Scholar) to Eknath Easwaran (Passage Meditation).