The Vedas are a group of Sanskrit texts revered in Hinduism, and going back some 3,500 years.  They represent possibly the oldest continuous textual tradition in the world.  Originating before the advent of writing, they were preserved, and indeed still are preserved, through a heavily formalized system of chanting.  There are several methods of chanting, but each serves to incorporate an error checking mechanism, by separating sound and sense.  For example, a sequence of words, ABCDE… will be chanted, in one pattern, as ABBAAB, BCCBBC, CDDCCD, etc.  Other patterns are more complex, but they all involve reversing word order, within sequences in which both forward and backward orders occur, thereby emphasising the sounds themselves.  Any error introduced by a novice will stand out like a sore thumb, as a sense-based slip will violate the sound pattern, and a sound-based slippage will destroy the sense.  Doing this collectively makes the whole process very robust indeed. To this date, the chanted version of the texts is considered authoritative.

The Wikipedia article on Vedic chant is quite thorough. YouTube has many examples for your listening pleasure.

In 2003, UNESCO proclaimed the tradition of Vedic chant a Masterpiece of the Oral and Intangible Heritage of Humanity.