We still use the 1940 Hymnal. What surprised me recently was to learn that the hymns don't end at #600. In more recent printings there is another section with hymns following the supplemental service material, up in the 700s.
Mine has a supplement from the 1960's, I think. I'll have to look in it and see what the numbers are.
In the very back there are note pages. In most books these are blank, but in this they are ruled with music staffs. I can just see a choir copying down some music that a choir director had written up on a chalk board. There was no such thing as copy machines in 1940.
There are some wonderful hymns in the "Post 600" section of newer printings (post 1970 I think). Examples: "Christ is Made the Sure Foundation" (Westminster Abbey by Henry Purcell), "Rejoice Ye Pure in Heart" (Vineyard Haven by Richard Dirksen). They also include some interesting examples of American Southern Harmony hymns like Wondrous Love (w/shape notes!).
Note also the Benedictus qui venit to the Holy Communion Services of Merbecke and Willan.