There is no real way to answer that directly
That will depend entirely on how often and for how long you listen to music. And the actual file size of the songs you are listening to, and by extension their length.
Assuming an average file size of around 6MB per song, and 3 minutes per song, you would be consuming about 20MB of data every 10 minutes. If you listen to 1 hour every day for a month, you would be consuming around 3.6GB data a month.
This of course can change depending on song length, and time listening, quality etc...
Expect no less than a couple GB of data every month for only 1 hour a day of listening regardless of quality.