What is The Symphony of Haruhi Suzumiya?

Sources:

https://www.animenewsnetwork.com/news/2009-02-03/haruhi-suzumiya-tv-anime-reportedly-to-relaunch-in-april
https://www.animenewsnetwork.com/news/2009-02-04/kadokawa-shoten-reportedly-says-april-haruhi-is-rerun
https://www.animenewsnetwork.com/news/2009-02-06/staff-for-renewed-airing-of-haruhi-suzumiya-announced
https://myanimelist.net/news/2711646
http://www.haruhi.tv/fanclub/special_event_gensou.html
http://www.haruhi.tv/fanclub/special_event_gensou_repo.html
https://haruhi.fandom.com/wiki/The_Adventures_of_Mikuru_Asahina_Episode_00
https://haruhi.fandom.com/wiki/The_Symphony_of_Haruhi_Suzumiya
https://www.animenewsnetwork.com/encyclopedia/people.php?id=55249
https://haruhi.fandom.com/wiki/Yuki,_Muon,_Madobe_Nite
Suzumiya Haruhi No Gensou, CD, LACA-5920
https://www.lantis.jp/release-item/LACA-5920.html
https://vgmdb.net/album/47228
https://myfigurecollection.net/item/59959