One of the biggest leaps for version 6 was its inline MIDI editing. It allowed producers to edit MIDI data directly on the main timeline using a piano roll or drum grid interface, eliminating the need to open separate editing windows and significantly accelerating the creative workflow.
: Introduced the ability to record multiple tracks of audio and MIDI simultaneously. Inline MIDI Editing
ACID Pro 6 offered comprehensive hosting for VST instruments and effects, as well as DirectX plug-ins. This opened the door for producers to integrate third-party synthesizers, samplers, and high-end processing suites directly into their ACID mixing console.