This depends on your computer. With a Pentium Core duo, 2.8 Ghz, and 2 gigabyte of RAM, users have reported running over 100 instruments at once as a VST plug-in Users with slower processors - like a 2 Ghz single core report about 30 instruments.

Your experience may vary depending on your settings, programs, configuration and other factors.

The ARIA Engine is designed to make use of the processing power of your computer and work best on modern CPUs. The faster your processor the better the libraries works.