It can further be explained that Bnei Yisrael (the Children of Israel) sang the song with great unity, as one person with one heart, just as they were later during Matan Torah (the giving of the Torah). This emphasizes that they sang the song "all together." The explanation is that during Yetzias Mitzrayim (the Exodus from Egypt), the concept of "Klal Yisrael" (the collective of Israel) was formed. Am Yisrael (the people of Israel) is not a collection of many individuals, but rather one collective entity. It is impossible for there to be division within it, as then the designation of "Klal Yisrael" cannot be applied. Only when they are united do they reach their highest level and glory. Therefore, they unified during the song, all together.