When searching our catalog, use the Advanced Search, and check the "Limit to Available" box. This will eliminate any resource where all the copies are checked out, damaged or otherwise unavailable. This is particularly useful when you're looking for a song that appears in lots of different scores.
Some of our databases, such as Oxford/Grove Music Online and our eBooks, are completely full-text, but many of our databases have a combination of full-text articles and citations only, which tell you where you can find an article without providing the full text. If you are too pressed for time to look in our print collection of magazines and journals or even to check a different database for electronic access, you can often limit your search results to those with full-text availability. Each database handles it slightly differently, although there are similarities in the same family of databases. Here's an example from Academic Search Premier from EBSCOHost, and it looks the same in EBSCOHost's Music Index and Business Source Premier.
If you're not finding what you need with using these limits, you might need to take more time. But let our resources do the work for you when they can.