Q: "How many levels of undo does Digital Performer now have?"

A: Digital Performer 4.x supports unlimited Undo/Redo. There are several new commands in the Edit menu to support the same single-step undo behavior of previous version, plus new commands to step forward and backward through the undo history. The Undo History window provides a complete log of actions and numerous features for navigating through the undo history and jumping to any point. Unlimited branching is supported, and an undo time line is also provided. Digital Performer also saves a permanent undo history for audio files that is saved with the audio file itself, allowing you to undo any changes that have been made at any time since the audio file was first created.

In other words, your entire undo history is saved with your project, so you don't lose it when you save or close a file. You can undo back to when the project was created months ago!