Amazon this evening said in a statement that the Kindle 2's text-to-speech feature for reading audiobooks will be strictly voluntary. The move will let individual book publishers decide whether or not individual titles can be read aloud by the e-book device and will change the book formatting to selectively disable the feature for those that object to it. The change follows objections from the Author's Guild which argued that the feature effectively violated the commercial rights of authors to charge separately for voiced editions of their books.

The online retailer maintains that the text-to-speech feature doesn't tread on the Guild's rights and believes that it would spur the growth of audiobooks by encouraging people to use the format. However, the company adds that it sees permission as a compromise between its own position and those of book publishers in the hopes that more will come to see the speak-aloud ability as beneficial.

"We strongly believe many rights-holders will be more comfortable with the text-to-speech feature if they are in the driver’s seat," Amazon says.

Critics of the Author's Guild have pointed out that the quality of the Kindle 2's conversion still isn't strong enough to effectively replace a professional audiobook performance and thus doesn't qualify as a threat to author's rights or to existing audiobook services like Audible. They have also warned that agreeing to restrictions sets a dangerous precedent which could lead to similar warnings about operating systems and third-party apps that achieve a similar objective, such as the text-to-speech features in Mac OS X and Windows Vista.