In perfumery a mixture that smells different from its components is called an accord. However the nose retains its capacity to analyse the accord in order to detect each component.
This is very stange.
Let us remark that the accord will be perceived as a smell of its own by everybody, but only the persons who know the ingredients will be able to analyse the accord.
Analysis of smell requires the help of the evolved part of the brain, particularly the orbitofrontal cortex and the language center.
I have met people who are able to detect the presence in a perfume of the smallest part of an essence that they abhor, rose or Frankincense for instance.
Their nose does not detect the smell of rose or frankincense in the perfume, there is too little of that in the perfume to be detected, I know it well enough, having composed the perfume myself.
What they detect is the emotion that these smells associate.
These persons did hate rose or Frankincense due to a trauma. They had been exposed to them in a situation of stress and distress and had memorized these smells associating them with the negative emotions lived during that situation.
Their nose acted as a detector, it detected the presence of the essence associated with distress and notified the danger they represented (according to their personal experience) by reproducing the record of the emotion.
The facts about the nose illustrated in these reflections are three:
The nose has a synthetic perception of scents, thousands of aromatic molecules are identified as a single odour.
The nose has an analytic perception of scents, and can be used as an instrument by the brain in order to split an odour in each of its components.
The nose can act as a gas chromatography instrument, informing us about the presence of some components in a scent that are of particular relevance for our survival.