Baby powder/talc smell: Usually based on white musks (see this article on classification/perception of musks and that one on synthetic musks) or orange blossom. The latter due to its ubiquitous use in baby products, imparting a feeling of both freshness and tenderness. For reference the actual Johnson's Baby Powder has traditionally relied on the combination of citrus-vanilla-lavender.
Banana note: A natural facet of some white flowers (particularly jasmine sambac or ylang-ylang), when the effect is an unripe, green banana, unpeeled. It's also common when there is a lot of benzyl acetate in the formula, which is in turn naturally found in jasmine, ylang ylang and tobira blossoms.
Band-Aid note: Usually a synthetic "oud/aoudh" base is responsible for this weird, medicinal effect.
Blood/metallic note: Due to 1-octen-3-one. Has an odour that is a cross between metallic blood and mushroom (see "cepes" notes in perfumery). Blood can be evoked via two aldehydes as well: decanal and nonenal.
Body Odour: see Sweat below
Caramel note: Usually a combination of vanillic notes (real vanilla pod orchid essence or vanillin).
Bad breath note: Usually caused by trimethylamine, fishy in low concentration, ammoniac in higher. (see also Fish note). Sulfurous notes from grapefruit in scent might also "read" as a bad breath note or body odour. Methanethiol (methyl mercaptan) is a constituent of bad breath and has a fecal scent (it is indeed found in flatus and in "asparagus urine", i.e. urine after eating asparagus).
Barnyard note: Usually there is a strong animalic note such as civet/civetone as well as indolic notes via jasmine or other white flowers. The horse note can be produced by presence of p-Cresol (a phenol) as well. A little hay (as in Chergui by Serge Lutens, the closest to natural hay absolute on the market) adds to the impression of a proper barnyard. L'Air de Rien for Miller Harris is a good example of "barnyard" scent via "dirty musks" and animalic notes.
Bread note: Due to 2-Acetyl-1-pyrroline (this is present in pandanus) and to lesser degree 6-Acetyl-2,3,4,5-tetrahydropyridine.
Cabbage note: Due to Methanethiol (also known as methyl mercaptan). Naturally occuring in nuts and cheese.
Cardboard/Old Books note: Due to salycilates (see more info)/"solar notes" and vanilla (the decomposition of wood pupl's lignin ~ a close relative to vanillin~ over time produces that effect natually in old books). Smell Dzing! by L'Artisan Parfumeur.
Cat Pee note: That intense ammoniac spray is due to blackcurrant buds, which have both butyric and sulfuric facets.
Celery note: Due to vertofix, a IFF molecule (methyl cedryl ketone) which smells like vetiver/leathery. It can therefore hide as "vetiver" and musky notes in a fragrance notes pyramid.
Cheese note: Butyric notes, like rancid butter (from βούτυρον/butyron, ie. butter in Greek), coupled with animalic notes such as civet/civetone. Frequent in some intense white florals.
Cotton-Candy (US)/Candyfloss (UK) note: Due to ethylmaltol, as famously used in Angel and Pink Sugar.
Cut grass: A sweet and green scent, usually due to triplal/ligustral (smelling like ligustra leaves) and coumarin (a material naturally found in tonka beans, as well as woodruff, sweet clover and cassia cinnamon). Also cis 3 hexenol smells like grass and is very common.
Curry note: Usually a combination of spices, one of which has to be cumin. It also includes coriander and sometimes "dirty" musks. See L'Autre by Diptyque.
Dentist's office: Cloves, cloves and cloves again! Dentists use clove for its naturally antiseptic properties. Several older Caron fragrances have a clove-y base and most carnation scents are traditionally built on a pepper and clove accord.
Detergent/Fabric Softener note: A great quantity of synthetic musks, especially "white musks" (see index) due to their ubiquitousness in detergents & fabric softeners thanks to their hydrophobicity (i.e. they rinse poorly and thus stay on clothes for long, which is the desired effect by the functional products industry). Cheap ambers such as Cetalox are also used in functional fragrances (i.e detergents), so presence in a fragrance can also give the association of laundry day. If the effect is acrid, it could be also due to dihydromercenol (the ingredient in many fresh aquatic men's colognes, see Davidof's Cool Water for instance) or lily of the valley. Lily of the valley (in the form of synthetics) is commonly used in detergents for the home as well as toilet cleaners thanks to its fresh, clean, green-floral aroma: witness Ajax White Flowers floor cleaner, which replicates the effect to a T.
Doll's Head: A combination of vanillin alongside heliotropin in smaller dose.
Earth (wet) note: This can be due to patchouli being dominant. Also patchouli coupled with oakmoss, but then the note is dryer and more bitter.
Feces/Fecal note: Usually due to indole (a constituent of white flowers, especially jasmine).
Felt-tip pens/markers: This is an effect of p-Cresol. Usually it's done in a "dry" context.
Fish note: There must be a trimethylamine note in there somewhere. At high concentrations, it can be ammoniac-smelling.
Fruity hard candy: Veltol gives a note of berries and caramel-like nuance(it increases the caramel effect and reduces the off cooked butter notes). It increases "creaminess" in both flavours (in lite products especially) and fragrances. You might also find Veltol in chocolate fragrances due to its creaminess.
Fuel oil/diesel: Cis 3 hexenol gives such an effect sometimes, although usually it's producing a green-grassy effect. Consider methyl benzoate as well, as evidenced in the opening of Jicky and Tubéreuse Criminelle.
Garbage note: The sickly sweet smell of rotting flesh/foodstuff is evoked by methyl anthranilate. Naturally found in bergamot, black locust, champaca, gardenia, jasmine, lemon, mandarin, neroli, orange, strawberry, tuberose, wisteria, galangal and ylang ylang. Of course the real corpse smell is due to two other compounds, not used in fragrances, cadaverine and putrescine.
Gas (natural) note: Although gas is primarily constisting of methane, it is the added compound tetrahydrothiophene which gives it its characteristic unpleasant rotten eggs odour.
Glue: This smell is a combination of heliotropin (synthetic heliotrope note with a marzipan facet), coumarin or anisic aldehyde. Styrax also has a faint glue aroma that reads as cinnamon-spicy.
Grape/Kool Aid note: Grape-fruity (concord grapes) is evoked thanks to methyl anthranilate. Dimethyl anthranilate is used to flavour Kool Aid. You might see this masked as a fruity note (berry) in perfumes. Sometimes has musty facets.
Greens bitter: Some pyrazines are responsible: 2-methoxy-3-isobutyl-pyrazine is the main flavour constituent of green bell peppers. Methoxy-methyl-, -ethyl- or-isopropyl-pyrazine increases the potato flavour of a potato salad while 2-methoxy-3-sec.butyl-, 2-methoxy-3-isobutyl- and 2-methoxy-3-isopropyl pyrazine appear in peas.
On the other hand, 2-methoxy-3-sec.butylpyrazine has been isolated from galbanum oil and has its characteristic bitter green odour profile.
Hair (dity) note: The culprit is costus root (do not confuse with cistus labdanum which has a leathery-ambery smell). Now restricted from perfumery, it is quite common in vintage perfumes (see Fille d'Eve by Germaine Cellier for Nina Ricci)
Hairspray note: Usually due to benzyl acetate. Among hairspray brands, some further aromatize their product with other aromata: L'Oreal Elnette hairspray for instance is particularly musky (in a pleasant ~to me at least~way)
Honey note: Either due to natural beeswax absolute in natural perfumery or -more commonly- due to mimosa & cassie absolute as well as cinnamic acid (used in the manufacturing of the methyl, ethyl, and benzyl esters for the perfume industry), which has a floral nuance to its honeyed note. Smell L'Instant by Guerlain in Eau de Parfum.
Horses note: see Barnyard note above
Leeks note: See Cabbage.
Melon/Watermelon note: Usually rendered by the immensely popular in the 1990s Calone aromachemical. (technically: methylbenzodioxepinone) . Unmistakeable, you know it well from Eau d'Issey and Aqua di Gio.
Metal/Cold Air note: Often due to helional, giving an impression of ringing cold air in some Northern steppe. Luca Turin describes it as "sucked silver spoon".
Mold/musty note: Dominant "dusty" variations of patchouli, sometimes coupled with carrot seed (which has a turnip-iris effect by nature). It can also surface in some incense variations with patchouli, such as in Messe de Minuit by Etro. Methyl anthranilate also might play a role, in the context of grape-fruity.
Mushroom note: See also Blood (1-octen-3-one) and look out for it in some gardenia compositions.
Nail polish note: Usually due to benzyl acetate, naturally found in white flowers.
Nail polish remover note: Due to methyl acetate.
"Old-lady" note: Due to powdery notes alongside woody ones or aldehydes (see more on types of aldehydes on this link). Too much iris can also give that effect in certain contexts due to its dryness. This is purely a cultural effect, because these happened to be popular smells in decades past, whose wearers are now "older ladies"! (For this controversial can of worms, read this essay).
Peach: Often due to gamma-Decalactone (referenced as C14 aldehyde, famously featured in Mitsouko). Peachy-apricoty scents can be rendered through jasmolactones too, and are actually preferred due to their fatty-creamy aspect.
Pear drops note (UK boiled sweet): A similar smell is found in ethyl acetate, a very evnescent, low-cost liquid used in perfumes as diluent and a common solvent in nail polish removers and decaffeinated coffee beans & tea leaves. It's worthy of note that it's the most common ester in wine, so the mental pear-wine link aromatically is not without cause.
Play-Doh note: Common lore wants it to be similar to heliotropin/heliotrope notes (affectionately referenced in iconic L'Heure Bleue by Guerlain). Etro's Heliotrope is a good example of this in action. I suggest that the modeling clay note is more wheat-almondy in nuance, a bit like marzipan but saltier, not classic Guerlain. Compare with Hypnotic Poison by Dior or Jaipur by Boucheron. Such a beloved, nostalgic note that it has entered a seperate creation by Demeter, simply called...Play Doh!
Pop-corn note: Due to 6-Acetyl-2,3,4,5-tetrahydropyridine, a common flavour used in pop-corn and tortillas.
Rice steam/basmati rice/jasmine rice note: Rendered through 2-Acetyl-1-pyrroline, a common flavouring in said products.
Rice powder/facial powder note: Often due to iris (either due to natural orris butter or violet-like ionones) as well as mimosa.
Rosy apple note: Due to damascones, materials analogous to ionones (which smell of violet/iris). Smell Knowing by Lauder or Coriandre by Jean Couturier to see them in action.
Tar: Due to phenols. Phenolic smells simply refer to tarry ones! Please note that "birch tar" is the pungent, leathery scent associated with Cuir de Russie type of scents (explanation on what Russian Leather scents are here).
Toast/Burnt note: This is due to pyrazines, compounds present in foodstuffs (see Greens Bitter above). Alkoxy- and/or alkylpyrazines can be added to coffee to increase the roast aroma, as well as other roasted foods (even meat).
Tomato note: Due to triplal (green leafy aroma) being overdosed, also green notes/cis 3 hexenal (similar with grassy greens).
Salty skin: Beautifully rendered through natural ambergris. Nowadays often replaced by synthetics.
Socks (dirty) note: Usually due to the presence of costus. Costus being restricted in current perfumery, this will be less and less a concern. The effect is apparent however in several vintage perfumes.
Suntan oil/tanning lotion/warm sand: If the fragrance or cosmetic has a floral-warm odour like the classic Ambre Solaire, sthis is due to salicylates (see this article for info on salicylates). Ylang ylang naturally contains them. You might also find this effect under "solar notes" in a traditional list of accords. If smelling of coconut, the classic Coppertone smell, it's due to gamma-Nonalactone (aldehyde C18) which is traditionally used in suntan lotions.
Sweat note: Common lore wants cumin to smell like sweat, but this is debateable as attested through research (Sweat has naturally sulphurous compounds, such as garlic, grapefruit and onion). Refer to Barnyard and Socks notes as well.
Urinal cake: Due to dihydromercenol (see also Detergent note).
Urine note: Phenylacetic acid is infamous for smelling like honey in large concentrations and urine in dilution. Miel de Bois by Serge Lutens is derisive for a reason...
Warm milk/warm pudding notes: A combination of vanillic notes, possibly with veltol or ethylmaltol if it reminds one of puddings or desserts off the oven. Saffron and mimosa also have some facets which are reminiscent of these, perhaps due to associations with edible notes.
Wine notes: Since ethyl acetate is the most common ester in wine, its presence in a perfume formula (which is common) evokes a wine-like effect (also see Pear drops). Some rose essences also have wine-y facets; witness Ce Soir ou Jamais by Annick Goutal.
There are also some more abstract effects which are caused by specific ingredients:
The "nose-hairs burning" effect is often due to synthetic woody-ambers, such as Ambroxan or Karanal, which smell like strong rubbing alcohol when in isolation. The "needles up the nose" effect (very sharp feel) can be due to lots of aldehydes in a very alkaline/soapy context: see White Linen by Lauder for that sharply fresh, sudsy effect. A seeming anaesthetizing of the nose can be due to a preponderance of ionones (violet notes). The too sour, too acid impression can be due to a very citric touch of hesperidic essences (from citrus fruits).
Usually the designation of something as "fresh" is considered a positive one, even though it might not relate to a specifically "fresh" family (such as aqueous/light floral/light fougere/citrus); analogously, "heavy" usually is used to describe a negative effect, again not relative to specific fragrance families but rather to "volume" of perfume, intense projection and radius of evaporation, especially when combined with more potent notes such as lush florals, intense mosses/woods or oriental/resinous notes.
In the end, getting to know the vocabulary of scent not only facilitates a common language reference among fellow fragrance enthusiastcs, but also enriches the experience itself, much like getting to know the parameters of art critique enhances the appreciation of art itself.
If you haven't caught on the Perfumery Definitions series till now, please visit: