Question about the French language?

In French, the word "the" can be used as le , la, or l'amour. I know that the l' is only used before vowels and to silent an h for example, l'hommage. I also know that le is a male form and la is a female form. However, I sometimes see la being used as a average sentence for example: "La nuit est longue." How do you get a female out of that? Here is another example, "La musique est dans mon coeur." To everyone who answers respectively , I appreciate your time! Thanks!