So I looked up some info on the Musicmaster.
"The
Fender Musicmaster Bass is a model of electric
bass guitar, produced by
Fender between 1971 and 1981.
As with its six-string counterpart, which was a stripped-down version of the
Fender Mustang, the Musicmaster Bass is a simpler version of the
Invalid Link Removed. It features a short 30 in (762 mm) scale. All of the Musicmaster's electronics are mounted onto a single piece of plastic.
Like many of Fender's other budget-priced guitars, the Musicmaster Bass used many surplus parts from other Fender models. The bodies were leftover
Invalid Link Removed bodies, while the pickups were six-pole guitar pickups, rather than four-pole bass pickups. Many players modified the bodies of their Musicmaster basses to accommodate
Precision-style double pickups or enhanced electronics. Woods used for the body were generally poplar, with maple necks and rosewood fretboards."
I guess I had heard that before, that the Musicmaster bass was used with bodies rejected for Mustangs. The biggest differences that made it a "student" or "budget" model was the use of strat pickups and less expensive electronics.
Maybe that helps?