Anyone know what an agogic accent is? (not sure if that's the correct spelling)

From wikipedia "An agogic accent is an emphasis by virtue of being longer in duration than surrounding notes, in a way that shifts their time of onset."
I'm afraid i wouldn't have a clue how to play it although it sounds like it has a similar effect to a tennuto.

I was told recently that it's a slight "sideways" (?) accent - so I presume that it's shown by a line over/under a note. But I'd never heard the word before. Just wondering if some of you clever people have?

Grove describes its use in, for instance, harpsichord and organ playing, where you can't vary the dynamic to make an accent. e.G As an organist I use different lengths and articulations of nominally equal crotchets to simulate dynamic variation.

Didn't know that that was what it was called, though!