で, を and に are incorrect in this context. That's why I just have to choose も.. I can't explain all of the functions of で but one is to describe a place where something (sing a song) is performed. 私は同じ歌を学校で歌いました。 学校(で) is a place. 私は同じ歌を公園で歌いました。　 公園(で) is a place. も not only means 'also' but is used to emphasize certain words. Your も emphasizes the number of times that person sang. I suppose the writer gets either surprised in a good way, or tired of listening to that person(= complaining), at least, the writer has some sort of emotional feeling about that person or the number of times. Since it's just an emphasis, without も, the sentence still remains correct as a sentence. あの人は同じ歌を10回、歌いました。 These も emphasize the length of time, distance and period of time etc. 私は友達と10時間も話した。 目的地まで、まだ10kmもある。 私は日本語を10年間も勉強している。 私はお菓子を10個も買った。