Where did you hear about (a website, a friend, an email)? Is it an app, a website, or a document ?
It is highly likely that this term refers to a specialized, niche, or local application, or a misunderstanding of a title in a foreign language (likely Italian, meaning "Musical Paradise Reader"). Lettore paradiso musicale 1.3.2
However, the phrase "Lettore" (Reader/Player) and "Musicale" (Musical) in an Italian context often appears in academic or archival materials. Where did you hear about (a website, a friend, an email)