Audiobook Music & Sound Effects

I'm seeking an experienced audio engineer to enhance a fiction audiobook.

Key tasks include:
- Adding ambient background music (classical, ambient, dramatic)
- Incorporating nature and fantasy sound effects
- Mixing and mastering for a polished final product

Ideal freelancers should have:
- Proven experience with audiobooks
- Strong skills in sound mixing and mastering
- A portfolio showcasing similar projects

Please provide samples of previous work and an estimated timeline.