Query: What technique were used to reduce inner-groove distortion?
Context: Through the 1960s, 1970s, and 1980s, various methods to improve the dynamic range of mass-produced records involved highly advanced disc cutting equipment. These techniques, marketed, to name two, as the CBS DisComputer and Teldec Direct Metal Mastering, were used to reduce inner-groove distortion. RCA Victor introduced another system to reduce dynamic range and achieve a groove with less surface noise under the commercial name of Dynagroove.