If you're looking for a song search engine that uses machine learning to deliver results, Cyanite is a top contender. The AI-based service is good for tagging music with rich metadata and for finding similar songs. It also offers keyword and free text search, so it's good for both pros and amateurs.
If you need a huge library to search, Audioatlas is worth a look. With more than 200 million songs and AI-powered search, it's easy to find music for a project or for personal use, which is why it's popular with content creators and filmmakers.