There are many benefits to taking an Open-Source approach to music, art or software. Here are a few:

• Cheap promotion - There are many Internet sites which will help you promote your Creative Commons or Open-Source works for free.
• Improved quality - popular Open-Source works are reviewed by many peers which tends to increase their quality.
• Public image - Successful Open-Source creators build a publicly viewable body of work and a reputation which can be used to "cash in" by selling services and related goods.
• Improved creative process - Creative people who share not only digital works but also the methods by which they create improve their process.