Apple introduced its fourth-generation iPod portable music players Monday with lower prices and longer battery life. The new models have up to 12 hours of rechargeable battery life, compared to about 8 hours with the current crop. The prices are $ 299 for a 20-gigabyte model and $ 399 for a 40-gigabyte model — each $ 100 less than their earlier counterparts. The new iPod versions are also thinner and have improved software features, including a quicker way to shuffle songs and a variable playback speed of audio books.

Apple introduced its fourth-generation iPod portable music players Monday with lower prices and longer battery life. The new models have up to 12 hours of rechargeable battery life, compared to about 8 hours with the current crop. The prices are $ 299 for a 20-gigabyte model and $ 399 for a 40-gigabyte model — each $ 100 less than their earlier counterparts. The new iPod versions are also thinner and have improved software features, including a quicker way to shuffle songs and a variable playback speed of audio books.