There are several different types of editions of scores available, especially for European and American Art Music before 1900. Each edition either represents an important snapshot in the documentation of that work, or it is designed for a specific type of use. Below are some of the most common edition types and terminology.
For more information on types of scholarly score editions, see the Grove Dictionary of Music & Musicians in Oxford Music Online.
There are often several different types of primary sources for any given musical work. In general, any edition or version of a score where the composer was closely involved can be considered a primary source.
Modern researchers do not always have to travel to an archive to find primary sources. Instead, we can use a facsimile. Facsimiles are photographs or scans of a primary source, and these can be reproduced and published as a physical score, a set of microfilm, or as an image in an online archive.
Scholarly or critical editions are commercially published editions that are edited by an important scholar or performer who is an expert in the study or interpretation of that composer's music. The editor studies the various primary sources available for a given work (autographs, copies, first editions, and early editions), and documents differences between them. They create an edition that attempts to be as close as possible to what the composer originally intended. The edition will often have critical commentary (often called "kritischer Bericht" in German) that documents measure-by-measure their editorial decisions.