If notes are at all important for you, if you can read music, you should learn to write it. It really doesn't take long if you practice it a bit, and making a simple melody and chords (presumably, they don't want a full score!) leadsheet shouldn't be anything difficult.
It's like words... What's the point of reading, if you don't learn to write?!
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An arranger is just a tool. What matters is what you build with it..!