Can you help me to find that project from Elektor magazine?
Many years ago I met a project on the pages of Elector called "Дelta Delay" that is a digital audio reverberator.But it so happened that I lost that number and now I do not know how to find this article.
The board appears as though it could be from the same era as the MN3002 'bucket brigade' IC. It was among the first digital delay devices. It created an audio delay by passing a charge from one capacitor to another.
More advanced chips have come out in years since (eg., SAD1024). I think they would make a more advanced audio delay/reverberation unit than the one you are searching for.
Possibly simpler to build, too.