ATRAC was developed for Sony’s MiniDisc format. ATRAC was updated with version 2, then version 3, version 4, version 4.5, and Type R and Type S.
The first major update was ATRAC3 (not to be confused with version 3 of original ATRAC) in 1999. 1
Not confusing at all 🤪
tbh that just reinforces my growing distrust of the direction they are headed