Hello Ed,
I understand from other users that the Nancy sample set is *extremely* CPU-intensive (especially due to the number of virtual pipes it uses simultaneously per real pipe, since it plays tremulant-affected samples at the same time as non-tremulant-affected samples, for cross-fading between them). Aside from disabling some perspectives or buying an even more powerful CPU, and assuming that you're already using a good-quality audio interface/ASIO driver, your two main options are:
- Make sure your audio buffer size setting on the 'General settings | Audio device ...' screen is set to to 512 (or try 1024 if it's already set to 512). Buffer sizes smaller than 512 are considerably more CPU-intensive.
- Reduce the polyphony limit setting. The polyphony limit exists to allow you to prevent the CPU from being overloaded. You might well find that you can reduce it by a moderate amount without any noticeable adverse effects on the reverb tails.