Online learning resources
You can get help on the internet to learn choral parts. We’ve generally recommended Cyberbass.com, who have synthetic instruments playing your part loudly and other parts quietly. But it appears that Cyberbass have changed their site in some way and many singers are finding it doesn’t work any more.
Our anthems are shown there as No 1 “Zadok” (all in one file) and No 2 “The King Shall Rejoice” (split up into movements). All found here.
Choralia is an excellent alternative, perhaps the best yet. They have Zadok the Priest and our Bach cantata BWV140 “Watchet auf…” , but their version of The King Shall Rejoice is in more than four parts — use only with care.
learnchoralmusic.co.uk is a less commercial site than cyberbass. It may be a bit more clunky in use, but you can download files and use them offline (you have to pay for that at cyberbass). Zadok and The King Shall Rejoice are separate, and there is a page for BWV140 “Watchet auf…”. However, this site downloads “midi” music files, and you may need to find a “midi player” app for your computer, smartphone or tablet. There’s more help with this at the site’s help page.
There is helpful stuff on YouTube, as well, of course. But as is common with that site, there is so much that a bit of filtering would help… later, maybe never!