Which term best describes music played "affettuoso"?

The term "affettuoso" translates to "affectionately" in English, and it indicates that the music should be played in a tender and expressive manner. This descriptor evokes feelings of warmth and emotional depth, encouraging the performer to convey sensitivity and gentleness in their playing. Thus, "tenderly" is the most fitting term to encapsulate the essence of "affettuoso."

In this context, the other terms do not align with the meaning of "affettuoso." "Quickly" conveys a brisk tempo, which would contradict the slow and expressive nature that "affettuoso" suggests. "Forcefully" implies a strong and vigorous manner of playing that is inconsistent with the delicate emotions associated with "affettuoso." Lastly, while "calmly" may convey a sense of peace, it does not capture the specific sense of affectionate warmth that "tenderly" embodies. Therefore, the term that best fits the description of music played "affettuoso" is indeed "tenderly."