2. Content-based Filtering
Content-based filtering uses metadata attached to the items such as descriptions or keywords (tags) as the basis of the recommendation. Metadata characterizes and describes the item. Now, when the user likes an item the system determines that this user is likely to like other items with similar metadata to the one they already liked.
Three common ways to assign metadata to content items are through a qualitative, quantitative, and automated approach.
Firstly, the qualitative approach is through library editors that professionally characterize the content.
Secondly, in the quantitative or crowdsourced approach, a community of people assigns metadata to content manually. The more people participate, the more accurate and less subjectively biased the metadata gets.
And thirdly, the automated way where algorithmic systems automatically characterize the content.
Metadata
Musical metadata is adjacent information to the audio file. It can be objectively factual or descriptive (based on subjective perception). In the music industry, the latter is also often referred to as creative metadata.
For example, artist, album, year of publication are factual metadata. Descriptive data describes the actual content of a musical piece e.g. the mood, energy, and genre. Understanding the types of metadata and organizing the taxonomy of the library in a consistent way is very important as the content-based recommender uses this metadata to pick the music. If the metadata is wrong the recommender might pull out a wrong track. You can read more about how to properly structure a music catalog in our free taxonomy paper. For professional musicians sending music, this guide on editing music metadata can be helpful.