125 musicians came together for a special tribute for the end of Shingeki no Kyojin. Kickstarter campaign raised $119,970 and the project was a big success. Q&A break down many of the technical aspects of it.
https://www.youtube.com/live/1zaTzvAEWeU
You don't have to purchase the album to experience Grissini Project's work. Although the audio is not of the highest quality, YouTube version can give you a taste of the masterpiece.