Choral Public Domain Library

As most people know, the "received version" of the Allegri Miserere is not only quite different from Allegri's original, but there have been many versions, virtually one for each generation of practice in ornamentation, ficta, abellimenti etc. I am looking for a particular one.

Sometime not long after the first widely-available recordings one was released (1970's?) purporting to "restore" the "proper" abellimenti. I heard it a few times but can no longer remember the group who recorded it. The characteristics I remember are (1) no high C, (2) a ficta C# resulting in a Neapolitan 6th resolving to D, probably in the 4-part section.

Does anyone have a lead on this? I would be interested in both a recording and a score.

[cross-posted from Musical Questions]

Partly answered in another place. For the sheet music (if this is indeed the version you require) you will have to google availibilty. IIRC the edition was prepared by Hugh Keyte.