The 8673 synthesizer generator doesnt have a build in tapedrive.
For this controlled adjustments a HP85 computer with some ROM's (Adv.Progr., Matrix, Plotter/Printer) and an HPIB-Card was listed in the service manual of the generator. So i think it was one or more basic program(s).
I know the problem with such old tape. Often the tape drives also make problems due to the rubber of the transport mechanic for the cartrigde.
HPL was the first "high-level" programming language for me in 1978. At that time i have had the possibility to use sometimes an HP9825A computer.
It was fantasic for me
Later on i have had an HP9836C and after that a HP Viper card. For that time the were great.
The hope is dieing at last. Maybe someone has copied or transfered the old tapedata to a more modern media (files).
One of my ideas was to translate the original program maybe to a python script.
But you are right for only one 8673 it's probable the better way to do the performance tests and calibration acordingly the paper manual.
At the moment i have two 8673: 8673M + 8673C