The Gemara records a three way machloket as to how they sang.
1) R’ Akiva says that Moshe sang phrase by phrase, and the people would repeat after each phrase Ashira LaHashem.
2) R’ Yosi HaGalili says that Moshe sang a phrase and they repeated exactly what Moshe sang.
3) R’ Nechemia says that Moshe started the shira, but they all sang together.
I have a question on Rav Nechemia’s pshat. How did they all know the words so that they could all sing together?
I was thinking that they all had some revelation of Hashem, thus making them all like Neviim for a short time. Therefore they all had Divine inspiration, including knowing what to sing. This idea works well with the next sugya which talks about how even (unborn) babies looked up and said Zeh Aili viAnveihu.
Does anyone know an answer to my question about R’ Nechemia pshat or have any comments? There are greatly appreciated.