I just checked "The Herbalist": in addition to the American or Sweet Elder, there is a listing for Dwarf Elder - "a shrub quite different from the true elder"... "The fruit is four seeded, resembling true elderberries, but seldom becomes fully ripe". Perhaps these are the red berries mentioned.
The flowers, berries and root of the true elder are used, but only the root and bark of the Dwarf Elder. Perhaps the cyanide is in the Dwarf Elder only.
I grew up eating ripe elderberries, and as far as I know, had no reaction to them. But then I wouldn't know what a little cyanide reaction would be, anyway. Does cyanide build up like arsenic? Does cooking destroy it? Did it the affect birds and the field mice and other animals that ate the berries? Or perhaps a once-a-year dose of cyanide kept parasites or other organisms at bay?
Any one have any info on this?