Final answer:
The violin was not a popular instrument during the medieval period; other stringed instruments like the fiddle or vielle were in use. Instruments such as the recorder, portative organ, and harp were commonplace in medieval music.
Step-by-step explanation:
The instrument that was not popular during the medieval period among the options provided is the violin. The portative organ, harp, and recorder were indeed used during this era, with the recorder retaining more or less its past form. The violin as we know it today did not emerge until the Renaissance. Medieval stringed instruments included the fiddle or vielle, which was an early bowed string instrument, but the violin had yet to be developed. Other popular instruments of the time included assorted wind instruments like various flutes and the pan flute, plucked string instruments such as the lute, mandore, gittern, and psaltery, as well as the dulcimer, which was initially plucked and later struck. The evolution of musical instruments was greatly influenced by the available technology, materials, and the practicality of transport and usage within the societal context of the time.