The International Music Score Library Project (IMSLP), also known as the Petrucci Music Library after publisher Ottaviano Petrucci, is a subscription-based digital library of public-domain music scores. It includes public domain and licensed recordings to allow for study by ear. The project, which uses MediaWiki software, has uploaded more than 495,000 scores and 59,000 recordings of more than 152,000 works by 18,000 composers.[4] IMSLP has both an iOS app[5] and an Android app.[6]