Breakdown of Me emocionó que los fanáticos cantaran.
los
the (masculine plural)
cantar
to sing
que
that / than
me
to me / me (direct object)
Questions & Answers about Me emocionó que los fanáticos cantaran.
Why do we use the imperfect subjunctive (cantaran) here instead of the past indicative (cantaron)?
Because the main verb, emocionó, expresses an emotion. In Spanish, when you express a personal reaction or emotion about another subject's action, that second action requires the subjunctive. Since the main verb is in the past tense, the second verb must also be in the past, which is why we use the imperfect subjunctive (cantaran).
Why is the main verb emocionó conjugated in the third-person singular if I was the one who was thrilled?
This verb works just like gustar. The literal translation is basically: That the fans sang thrilled me. The entire second clause (que los fanáticos cantaran) acts as the subject of the sentence. Because a clause counts as a single abstract concept, emocionó takes the third-person singular form. The pronoun me just tells us who received the emotion.
Could I use the present subjunctive (canten) if I am still thrilled about it today?
No, because of the sequence of tenses. The main verb (emocionó) is in the preterite, anchoring the grammar of the sentence in the past. Even if you still feel the thrill right now, Spanish grammar rules dictate that a past-tense main verb requires a past-tense subjunctive verb in the dependent clause.
Could I say cantasen instead of cantaran?