Lyric discussion by donaldheil 

Cover art for Listen lyrics by Tears for Fears

Ok, here's the thing. I'm a born spanish speaker, and I've listened to this song since it was released back in 1985. Honestly, I don't find any hint of spanish language in the verse that it's repeated over and over in the last part of this song. I've always assumed that it was a dialect o language unknown to me. As someone has pointed out, there's one (even three) too many syllables to fit what's supposedly being sung. It's now that I got (at last) a little curious that I find the theory that this is spanish spread all over the internet. Until someone comes up with an official source for this, I'll think that this was just someone making up the words and so starting the wrong theory.

I agree with ben6821 that it's an instrumental song. More on this point later.

I also agree with @donaldheil–I've never thought it was español (or any actual words) being sung–I always thought it was silly, onomatopoeic, nonsense sounds. Nonsense, but specifically attempting to mimic the rhythm of the percussion being played–sometimes simultaneously while the onomatopeia was being spoken:

boom-dee-al-uh-chick-uh-nack-uh-ko-ko-say boom-dee-al-uh-chick-uh-muck-uh-ko-ko-say boom-dee-al-uh-chick-uh-nick-uh-ko-ko-say (I can't quite make out the 'nack,' 'muck,' 'nick' sound)

The percussion, playing over and over, has the same number of counts, and has much the same rhythm as the spoken onomatopoeia. The...