Copyright seeks to balance author and public interests by protecting the expression of ideas but not the underlying ideas themselves. Copyright protects works that are fixed in a tangible medium and provides authors with a bundle of exclusive rights including reproduction, distribution, public performance, creation of derivatives, and digital audio transmission. Copyright duration for individual works is the life of the author plus 70 years. Mechanical royalties from streaming services are typically a fraction of a penny per stream and must meet certain thresholds to earn substantial amounts. Fair use is an exception that allows limited unauthorized use of copyrighted works for purposes like education or commentary.