Why is the word bailar pronounced baillar?

Question

that's what i seem to hear in music

Answer 1

You're hearing wrong.

Answer 2

It seems you heard a different word.

The Spanish word "bailar" ("to dance") is always pronounced  / bah-ee-LAHR /.

Answer 3

Think about it, depending on the word, in English we can pronounce an L like a LL.  And if Bailar was said like Baillar it would take on a "y" or "j" sound and not an "l"