Swap used with ample RAM

Hi,

If anyone knows why Lion 10.7.4 swaps to the HD in the following conditions, please let me know:

24gb RAM in Mac Pro 2009

Right after boot, I load a large sample library template and watch the memory usage take off in Activity Monitor. It stops at 6.48 Free (green) and 17.51 Used.

Towards the end of the loading time, I get Page Outs = 52kb and Swap Used = 1.3mb.

I then load Cubase. It stops at 6.07 Free and 17.92 Used, with Page Outs = 205kb and Swap Used = 5mb.

Further work in Cubase doesn't result in any swapping at all.

Out of curiosity, why is OS X swapping to the HD when it has more than 6gb of free RAM?

Thanks.