Распевает = just "Sings" ("Warming up" is wrong context here)
Так не спеть тебе, француз! = You will never sing like this, frenchman!
Как затянет, как зальётся = all these words refer to the verb "sing", so the whole this phrase can be translated as "When russian people start to sing their songs"
Русь и в песне-то могуча, = Rus is mighty even when singing,
Широка и глубока, = it is wide and deep,
and so on ;)
His brother's name was Jubal; he was the father of all
who play stringed instruments and pipes. (Genesis 4:21)