Final answer:
The Studer A80 tape machine was the workhorse for recording projects from 1965-68 due to its high-quality sound reproduction and reliable performance.
Step-by-step explanation:
The tape machine that was the workhorse for recording projects from 1965-68 was the Studer A80 tape machine. It was widely used during that time period in professional recording studios. The Studer A80 was known for its high-quality sound reproduction and reliable performance, making it a popular choice for recording projects.