I'm not seeing this option on the Tools menu:
PRE-LOADED SET LISTS
In order to improve song switch times you can instruct Cantabile to pre-load all songs and racks used in the set list:
From the Tools menu, choose "Pre-load Set List" to toggle this feature on or off.
Whether to pre-load a set list is stored as a property of the set list, so you can have some set lists pre-load and some load on demand.
Depending on the plugins you're using, pre-loading a set list may require considerable RAM. You can mitigate this by sharing plugin instances across multiple songs by loading them into racks and using the same rack in each song.