Finally, I couldn't finish this feature without mentioning battery life. Depending on your player, the bit rate of the file and the audio format type, your player's CPU will be working at different rates.
There are few hard and fast rules governing this battery life, unfortunately. I could run a (forgive the pun) battery of tests on one player here, and you'd probably experience completely different results with yours. But as a general rule, you can expect larger files (such as losslessly-encoded files) to drain batter life quicker, and the more complicated codecs (AAC, Ogg Vorbis etc) are also likely to result in lower battery life than the quoted figures, which are normally based on 128kbs MP3 files. Bear in mind also, that for iPods, you're not comparing like with like when it comes to battery life figures as Apple quotes times based on 128kbps AAC files played on loop.
Hard disk players are affected more by file size. Normally a hard disk player will spin up, then load a track completely into a memory buffer before playing it. With a Flac or losslessly encoded track, however, that's not normally possible with tracks occupying 20MB and above. Part way through a track the player will have to then go and get load more information. The end result is more work for the hard disk per minute of music listened to and, therefore, lower battery life.
There's no doubt that compression methods have changed the way we experience our music forever. It has forced the music industry to wake from its comfortable slumber and ask serious questions about what consumers want, rather than what they think we want, and it has freed listeners from the shackles of physical media.
With storage falling in price by the week and the bandwidth of our Internet and network connections skyrocketing, there may come a time when we don't need music compression technology as we once did.
Until then, however, it's worth knowing a little more about such a talked about subject. And, hopefully, having read this feature, you're now a bit better informed and will be able to hold your own during those geeky arguments down the pub on a Friday night.