What is it?
Mixes the contents of the Clipboard with the current selection.

How to use it
If the selection is longer than the Clipboard's sound, it will mix the Clipboard's entire sound.  If the selection is shorter than the Clipboard's sound, it will mix as much of the Clipboard's sound as room allows.  Paste Mix has the following two parameters, Clipboard amplitude and Document amplitude.

The Clipboard field can have a range of 0 to 100%.  It controls the amplitude of the sound in the Clipboard.

The Document field can have a range of 0 to 100%.  It controls the amplitude of the sound in the document.

Notes
See "Show Clipboard" for more information.