It's safe to say the music industry is in a transition period, but one thing that's not going anywhere? iTunes.

iTunes has quickly taken hold of a good portion of the entire music industry: it accounts for 25% of all music units sold in the U.S., digitial or otherwise, up from 21% in 2008, according to NPD Group.

And no surprise here, iTunes has an especially firm grasp of the digital music market--it's responsible for 69% of consumer downloads, followed directly by AmazonMP3 with just 8%. With its upcoming iTunes 9 and its rumored social media integration, that grip will likely only tighten.

The growth of the digital music market is impressive--it shot up from 20% of the music market to 35% in just two years. It's definitely good news for the environment, and could be a good sign for the music industry overall--more people buying music online might mean less people are illegally downloading music online. And if the digital music market really takes over, that will be a huge cut in manufacturing costs for companies.

We still have a ways to go, though. Most Americans are still getting their music from CDs, which hold 65% of the market share (Wal-Mart accounting for 20%, leading the physical market). And let's be honest--radio sites like Pandora and the ever-present lure of stealing music make it hard to shell out any amount of money for music.