How many composers have written a Sonata No. 3?
Musical works often share title characteristics (form, instrumentation, numbers, keys, opus numbers) with other musical works. Each catalog record is tagged with the fullest combination of these characteristics so that difference forms of a musical work are grouped together (more on this below), but also so that individual works are separated out even if they share titles.
Each score is tagged with its genre or form and other work information (key, opus or catalog no., and instrumentation). If the composer has written more than one work in a particular form, then the form tag is made plural.
For example, try searching for Symphonies instead of Symphony.
The title tags added to each record can be searched. They follow a standard format: FINK (Form, instrumentation, number, and key). For Beethoven's Ninth, that tag reads: Symphonies, no. 9, op. 125, D minor.
Many of the big score publishers are located in Europe (where much of the music in our collection was originally written). This means many scores are published in German, French, Italian, and other European languages in equal measure with English. You may want to find The Marriage of Figaro, but the publisher issued it as Le Nozze di Figaro or Diedes Figaro.
There's a big difference between looking for opera The Marriage of Figaro and looking for the aria "Voi Che Sapete". Songs and movements that are tucked inside of larger works can be tricky to find, especially since they are often published as arrangements in collections (e.g. 24 Italian Songs and Arias). To find songs that are published as part of a larger work, like an aria in an operatic vocal score OR a song in a collection, use a phrase search.
Phrase searching is a technique where the search terms are placed in quotation marks so that the search engine or catalog is forced to find those words as a string. For example, if you were searching for the song "I feel pretty" from West Side Story, putting I feel pretty into the search box allows the catalog to pull up any record that includes the words I or feel or pretty. Entering "I feel pretty" with quotation marks will force the catalog to only return results that have that specific phrase.
Be aware that not every collection or work with individual songs included will have a list of all the songs in the catalog record. For example, a vocal score of La Traviata will not list every aria and recitative in that opera in the catalog record. But if you KNOW an aria is from Traviata, then you can search for a vocal score of the entire opera and expect to find the song in its original key there.