Over the years, across very different perfumes, the same accord kept appearing. Then disappearing again. A precise accord, and I had no idea where it came from. 
It would show up, always the same, tucked into a formula, quiet, almost incidental. Then it would vanish completely from the next creation, replaced by something else. Later it would resurface somewhere else entirely, in a context that had nothing to do with the last one. 
I wasn't looking for this accord. I simply recognized it when it appeared. 

Why does the same patchouli seem to change personality? 

Patchouli is usually summed up in a few words: woody, earthy, sometimes chocolatey. Those words aren't wrong. But they say almost nothing about what actually interests me in this material. 
Every time I use patchouli, it seems to behave differently from one formula to the next. Not because the raw material itself changes; it's often, quite literally, the same patchouli. What changes is what it does once it's surrounded by other materials. 
For a long time, patchouli's real job was modifying other materials rather than being smelled for itself. That was a quiet, background role, before it became a signature in its own right in certain contemporary trails. And that background role never really went away.

Why patchouli never plays the same role twice 

In Neverose, sitting underneath a centifolia rose (the "rose de mai"), patchouli barely announces itself. And yet, take it out of that powdery rose context, and it's what gives the flower its foundation. It doesn't add a recognizable smell; it adds a depth and a tension the floral heart wouldn't have on its own. 
In The Beast, on the other hand, a leather-chypre structure, patchouli takes on a far more assertive role. It shapes the perfume's darkness directly, its density, its grain, its relief. Here, you smell it. It's the main line running through the whole composition. 
In yet another register, at very low concentration, patchouli can become a simple blender — a material that brings two other ingredients closer together without ever announcing itself. It tints the woods with a faint nuance, without giving the composition any recognizable patchouli smell. 
Three contexts. Three completely different functions. None of these descriptions contradicts the others — they simply describe what patchouli does, not what it is. 

When patchouli disappears... but keeps working 

The accord that had been following me for years came from exactly this: patchouli's ability to reshape how another material is perceived. In this case, a musk. 
So I ran a methodical series of trials. Working through about twenty different musks, I found the one that produced this effect: Ethylene Brassylate. Paired with a very small proportion of patchouli, the exact effect I'd been chasing suddenly appeared. 
Patchouli's camphoraceous facet disappeared entirely, and the musk gained a woody, almost masculine depth it didn't have alone. Patchouli densified the musk, giving it a woody-earthy shadow and that distinctive fine grain, without ever becoming identifiable itself. What was left was a structured musk. 
The accord I'd been chasing for years was finally there. 

What Patchouli Taught Me 

It's this capacity to disappear as a smell while still organizing the entire formula that makes this material so fascinating to work with. 
Patchouli is sometimes at its most influential exactly when it stops being identifiable. I don't think of patchouli as a smell so much as a material capable of quietly transforming an entire formula. 
Decades after its rise to popularity, it's no coincidence that patchouli remains one of the most fascinating raw materials in a perfumer's palette.