In the early 2000s, the digital audio workstation (DAW) landscape was a very different place. Pro Tools was the undisputed king of big-budget studios, Cubase was mastering MIDI, and FruityLoops (now FL Studio) was seen as a toy for bedroom beatmakers. But nestled in the middle of this ecosystem was a piece of software that fundamentally changed how electronic music and sample-based composition were made: .

Version 4.0 was particularly significant because it was the last major version released by Sonic Foundry before the Sony acquisition, though it is often referred to as "Sony ACID Pro 4.0" due to Sony's long-term stewardship of the brand. Key Features of Version 4.0