To make it even more confusing Fromwithin
mentions the "Fairlight CMI" first launched acording to my handbook in 1979 though UNTIL 1982 and the introduction of the Musical Instrument Digital Interface commonly called MIDI was introduced synths had been limited to onboard appregiator devices.
By its definition a tracker is able to produce highly quantised rigidly structured , music from its own onboard bank of sampled sounds & its controlled through an alpha numeric scrolling display GUI.
So by definition a punched disk or waxed paper PLAYER piano or fairground organ would be its true ancestor.
I certainly suspect you are refering to the computor based trackers as opposed to sequencers so I wonder if there was ever a music program for the ZX81 ?
Even if it only played "happy birthday" in mono from a prewritten line it would count
Or would it ?