If you can't play it, you can't hear it. There are so few musicians, that can randomly sing modes off the top of their heads. In 30 years I've never met anyone that could sing modes without instrumental training. It may be possible, but I've not seen nor heard it. Remember, when practising scales on the guitar, attempt to "sing" them as you go or play along. This will create another world, and options, and is especially useful in college type courses. A very major lesson I learned, fortunately early, in my musical journey. Listen to a truck horn, not my singing.