Excepting extreme cases, such as the poster that made inquiries here a few months ago about managing his 200,000+ song library, the size of your iTunes library should not have much of an impact on the software’s performance. Unless Apple, or Cassidy & Greene—the company that developed the original SoundJam MP software before Apple acquired the code base—, built iTunes upon a very poorly designed database engine, very little of your physical music library (the actual song files) should actually occupy memory at any given time. Unfortunately, by design good databases tend to be very disk-intensive and that is often the source of performance issues as the data set grows.

For the most part iTunes should only have the core application, any supporting helper files (all the little things hidden away in its package) and your actual library database file loaded into memory much of the time. In addition to that, any song files currently being accessed, such as the currently selected or displayed song or those visible in CoverFlow, may be loaded in memory; this would be particularly true when you are playing music. Even when idle, iTunes very likely allocates a minimum amount of memory for loading songs into a buffer to minimize the demand on your hard drive.

I have a rather large (physical) library, 69.88 GB, but despite being extensively tagged and including custom scanned album art, the actual library file is only 26 MB. Right now iTunes is only using between 220 and 240 MB on my Mac idle. Take away 131 MB for the contents of the iTunes 7.7 package—the actual application is only 31 MB—and another 26 MB for the actual library database file and that leaves about 63 to 83 MB free for content. If you were to go by the assumption that the average song is 4 minutes long, there is enough of a buffer to load 13 to 18 songs into memory at the 160 Kbps bit rate at which my collection is ripped (4.6 MB per 4 min. song); CoverFlow displays 17 covers.

Virtual memory is another matter and according to Activity Monitor, iTunes is using in excess of 640 MB of virtual memory. Virtual memory is space allocated temporarily on your hard drive and given the capacity of the average laptop drive, particularly in the PowerBook era, and that is very likely where your problem lies. Hard drives are much slower than physical RAM and if your PowerBook’s drive is getting pretty full that leaves iTunes with little room to breathe.

You have a few options here. The first option is to add memory to your PowerBook if it is not already maxed out. The more physical RAM you have, the less iTunes should need to use virtual memory to a point. The downside is that adding physical RAM may only do so much because like most databases, iTunes is very disk-centric in its operation.

The second option is to reduce the bit rate of your music in order to create smaller song files. Unfortunately, going that route will result in a number of strong negatives from having to re-rip/re-acquire your entire collection to significantly degrading the audio quality of your music if your songs are already at a relatively low bit rate.

If you are close to or have exceeded filling 85 to 90 percent of your PowerBook’s hard drive capacity then a hard drive upgrade is in order. To avoid a trip to a certified Apple service center, the easy fix in this scenario is to move your library to a larger capacity external drive, preferably connected via FireWire.

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“Cannot run out of time. There is infinite time. You are finite. Zathras is finite. This is wrong tool.” 2.3GHz Power Mac G5/8GB/2x1TB HDD/OS X 10.4.11/30-inch ACD, 60GB iPod (Color)