The initial news and cover art were released in late May on the various Disney Music Emporium media sites (see, for example, the news on its Facebook page: https://www.facebook.com/DisneyMusicEmporium/photos/a.1417819401816272.1073741828.1417567548508124/1850095375255337/).
Further details on the set can be found on the WDW News Today website (http://wdwnt.com/blog/2017/05/d23-expo-2017-disney-music-emporium-returning-album-signings/), where Jesse DeRosa wrote on 26 May 2016:
Disney Music Emporium, a pop-up store that sells collectable Disney music-related products, will be returning to the D23 Expo 2017. During the event, fans will be able to purchase new limited music releases from various Disney artists and composers.
Walt Disney Records The Legacy Collection Robin Hood, a two-disc set, will be released for the first time during the expo. Disc one of the collection includes songs and score from the film. Disc two includes unreleased demos and bonus tracks performed by Louis Prima. The CD collection contains liner notes, as well as a 20-page booklet featuring new artwork inspired by Robin Hood from Lorelay Bove, a visual development artist who’s worked on various Disney films including Tangled, Wreck-It Ralph, and more. Those that purchase the collection will receive a special lithograph featuring the back cover artwork, though there will only be a limited quantity available.