I hate questions about "Modal Music" because nearly all the time, the discussions just make the question more confusing---there are a couple of reasons for this--

First, as has always true in the history of questions and answers, posts from people who don't actually know the answer, but think they do--Second, the people get confused because "Modal" is used in at least three, maybe four, completely different ways, and the discussion breaks down because no one can figure out how what anyone else is talking about fits in with what they are talking about--Third, the person asking the question doesn't know enough about music to make any sense out of the answers, anyway--It's enough to make a person run screaming from the room whenever the word comes up--But I won't--

Here is the simple answer to the question--The music you are listening is modal if it has no chord changes in it--yep, it's that simple--you don't have to know the names of modes(and, you couldn't recognize them all if your life depended on it--there are literally thousands of them)--

If you want a better aural illustration--and have Limewire or some other P2P file sharing program, search for these two versions of the same song: Andy Stewart's "The Green Hills of Tyrol"(also called "The Scottish Soldier" and any version of it by a Highland pipe band--listen, and you will know-

Modal music tends to have drones instead of chords--which are usually either or both the first and fifth note of the scale, and which ring through the entire course of the tune--

Real modal music uses untempered, or uneven scales--which means that the steps between note are not equal--so the perfect fifth and fourth intervals that are needed to construct chords don't really exist for a lot of the other notes in the scale--

Real modal music doesn't use vertical harmonies(the sort that occur in chords), either--

Now it is certainly possible to play modal melodies on a tempered scale, and it is possible to harmonize them, but then, even when they have "modal" features(like using a phrygian scale) they have been modernized are not really modal any more--

Of course, using the word "modern" is confusing too, because a lot of progressive jazz is modal, and so is a lot of funk, rap, and contemporary R&B music--so they key is to listen--if you hear a chord shift, from tonic to dominant, it isn't modal, if you recognize that the chords move through the circle of fifths, it isn't modal--but if everything stays in the same tonality(even if sounbds like it should change) it is modal--