At the annual meeting of the Network of Apostolic History, the earliest known sheet music edition of a (New) Apostolic hymnal in German was made available to interested researchers. It is the first edition of sheet music for the Apostolic Songbook of 1898, which appeared in 1900 but was not widely distributed. It was intended for four-part choral singing as well as for accompaniment by organ or harmonium.
German Hymnal
New Apostolic Hymnal from 1925 online again
For many years, the texts of New Apostolic musical literature (such as the choir songbook, the “old” New Apostolic hymnal, the public domain parts of the 2005 hymnal of the New Apostolic Church) could be accessed via the website nak-gesangbuch.de. However, the operator of this site passed away some time ago and the site is now no longer accessible.