Del mundo Salvador: In everyday speech or writing, you'd be much more likely to say "Salvador del mundo" for "Savior of the world." In music, however, there's considerably more latitude with word order to get the desired rhythm.
Tornad: Like regocijad, this is a plural-you command. Tornar typically means "to convert" or "to turn into," and it is used most frequently in a religious context. As you may have noticed, the vosotros imperative form of the verb is made simply by changing the final r of the infinitive to a d. And this is always true — there are no irregular verbs for this form.
En unión: Although this phrase could be translated as "in union," a better translation would be "in unity."
Loor: This word is rare enough you won't find it in smaller dictionaries. It means "praise."
Resonaré: Resonar means "to resound" or, more poetically, "to echo."
la maldad vencida es: This is another case of poetic word order. In everyday speech, you'd more likely say, "La maldad es vencida, "evil is overcome."
Bendición: Blessing (ben- = good, -dición = saying).
Quitó: Past tense of quitar, to remove.
Maldición: Curse (mal- = bad)
Señor: Although this word is often used as a courtesy title meaning the equivalent of "Mr.," it can also mean "lord."
La libertad tú le darás: This and the remainder of the song is an example of personification. The pronoun le usually isn't used to refer to things, only to people. But here it refers to Israel, which has been personified. A fairly close translation of this line to English would be "You will give her liberty, and You will be her God," with "her" referring to Israel.
