YOU SAID:

Many mumbling mice were making merry music in the moonlight mighty nice

INTO JAPANESE

多くのぶつぶつネズミは月明かりの下で陽気な音楽を作成していた

BACK INTO ENGLISH

Many grumpy rats were creating hilarious music under the moonlight

INTO JAPANESE

多くの不機嫌なネズミは、月明かりの下で陽気な音楽を作成していました

BACK INTO ENGLISH

Many grumpy rats were creating hilarious music under the moonlight