RILM Abstracts is an attempt to index all significant music literature since 1967, when it began publishing. As such,RILM indexes not only periodicals but also books and dissertations. The online version includes the entire database back to 1967. RILM is very international in content, including articles in hundreds of languages, including Aramaic and Catalan. In addition to citations, RILM includes abstracts (brief summaries) for most items. An abstract can be very helpful when you are trying to determine whether an item is relevant to your research. Abstracts are also searchable.
RILM does index some smaller items such as reviews, columns, and editorials (particularly in scholarly journals), but it concentrates on significant writings, so Music Index is often better for reviews. Although RILM does not itself contain any full text, many citations are linked to full text found in other databases such as JSTOR, Academic Search Complete, Lexis/Nexis, and the Electronic Journal Center. Some of these links are obvious and direct, but some are more hidden. Look for links that refer to LinkSource, which should (theoretically) find full text in any of B-W's databases. For (almost) definitive information on which periodicals BW owns, use the A to Z journal finder system.