When playing audio and it sounds like it is starting and stopping quickly, it could be because the computer is over tasked due to other programs running at the same time. In addition, your computer may not be powerful enough to mix the audio. Always shut down as many unnecessary programs as possible. It may even be advantageous to temporarily shut down your virus software. (We do not recommend doing this unless you have done a full scan and are not connected to the Internet.)
Pianissimo has to work harder as it mixes more notes.
Try increasing the buffer size or the number of buffers in the Sound Device Preferences if your are in Wave mode. If you are in ASIO mode, try a different ASIO driver or go into the ASIO driver's mixer and increase the latency. If you are in WaveRT mode, try increasing the latency time.
Always make sure that you have the latest drivers for your sound card. Visit your sound card manufacturer's website to see if there is an update.
Also, see the important sound setup page.