Digital music itself is a compression of analog music. The size of the digital file depends on the sampling bitrate. The higher the number, the better the quality. 128kbps is an okay bitrate for most songs. It won’t appease the audiophiles out there, but serious audiophiles shouldn’t be using digital music too much!
Back to the point, you can use iTunes to decrease the bitrate on your music, thus saving hard drive space on your computer and on your iPod. Instead of creating the 128kbps files just for your iPod or iPhone, you can make the change permanent in iTunes. The process is a bit different though.
First, you’ll want to check that you don’t have duplicate files in iTunes. Go to File > Show Duplicates. Make sure your songs are indeed duplicates, and delete all the extra files (if you have any). This will be important later.
Next, you’ll want to make sure your conversion settings are set to 128kbps. To do this, go into preferences, select the general tab, and go to import settings. Choose “High Quality”, this should set it to 128kbps stereo.
Now, you’ll have to create a smart playlist. This will collect your high Bit Rate songs. Go to File > New Smart Playlist. In the first drop-down menu, choose “Bit Rate”. In the second drop-down menu, choose “Is Greater Than”. Then, make sure the number in the box is 128. Then, click the + button. In the first box, choose “Media Kind”, then “Is” and finally, “Music”. Press OK.
Change the Untitled playlist to whatever you want. I recommend “High Bit Rate Songs”.
Make sure that all the songs in there are high bit rate songs. To do this, right click (or ctrl click) the bar with the titles “Name”, “Time”, “Artist”, etc. A list should come up, make sure “Bit Rate” is checked. This will show the bit rates for the songs. Then, click at the top, to sort. Make sure all the bit rate numbers are greater than 128.
Now, select all the songs, right click (or ctrl click), and choose “Make AAC File” (or something like that). This will copy and convert your song to 128kbps.
Now, since it copied your songs, you’ll want to get rid of those high bit rate ones. Go to the Music Item on the left (to show all your songs). Then choose File > Show Duplicates again. Make sure the “Bit Rate” column is still there, and then sort your music. You should be able to select all the songs that aren’t 128kbps, and delete them (it is wise to double check though).
Your Smart Playlist should be empty now. If it’s not, make sure you deleted the right files, and you’ve followed these directions to the T.
You should have reduced the size of your music library by a lot, and syncs with your iPod or iPhone will be quicker as well. And, unless you have excellent hearing, you most likely won’t notice a difference in sound quality. But you can always keep both versions of the songs you like, and skip syncing the high bit rate songs with your iPhone or iPod. It’s up to you what you do with your music. But now, you have the option of having a smaller library, without getting rid of any of your music.