"Not limited to strong perfumes of questionable taste, musk is in fact the basic ingredient of practically all perfumes, from the most expensive and refined French florals to the sleaziest reek of high school hoochies. Everything in your medicine cabinet contains musk: soaps, shampoos, powders, cosmetics, bath oils, even your toothpaste. It is an ingredient in household cleansers, laundry detergents, insect repellents, and almost every other commercial product that requires fragrance - including food. Does the label say "artificially flavored?" Musk is added to fruit flavors, vanilla, chocolates, licorice, hard candy, chewing gum..."
So where do these musks come from and what are synthetic/white musks?
Short History of Musk Use
Musk is the essence coming from a glandular secretion of the male Tibetan musk deer (Moschus moschiferus L), considered an aphrodisiac (as well as a spiritual fragrance in the Muslim world) in the past. It also fixes and balances a composition , refining it in the most plesasurable and sensuous way and allowing floral and resinous ingredients to flourish in it. Its first historical appearence is in the 5th century BC when it is mentioned in the Talmud (Brachot 43.) as an animal-based fragrance. Despite mentions of the supreme smell of the panther, the creature with the most divine scent imagineable according to the ancient Greeks, no reference per se is made in classical antiquity. In the 6th-century Greek explorer Cosmas Indicopleustes references it as a raw material of Indian origin. It took the Arabs and Byzantine perfume makers for it to rise as an aphrodisiac especiall during the height of the Abbasid Empire. The spice and silk route soon took the aromatic essence aboard and the string of languages that reprised the Sanskrit muṣká (denoting testicle, the source of the musk pod) ~via Middle Persian mušk, Late Greek μόσχος (moschos), Late Latin muscus, Middle French musc and all the way into Middle English muske~ is a journey into its aromatic signposts. In the 1970s musks soared: "In response to the "back-to-nature" ethos of the hippie movement, American perfumers on both coasts sought alternatives to traditional French perfumes. Around 1970, both The Body Shop* in Berkeley, CA, and Kiehl's in New York City introduced single-note "essential oil" fragrances". 
*In 1987 The Body Shop was taken over by a huge English firm of the same name, taking over the Musk oil that was synthesized in the 1970s and re-introducing it as White Musk, which is comprised of Galaxolide (7,7%), Tonalide (1,6%) a little Cashmeran (0,1%)for a total of 9.4% of white musks.
Origin and Scent of Natural Deer Musk
The musk deer (moschus moschiferus) is a small, inofensive creature living in Pakistan, India, Tibet, China, Siberia and Mongolia and only the mature male can produce musky odour in rutting season. The best quality musk used to come from Tibet (Tonquin/Tonkin musk) and China, while products from India and Siberia were considered of inferior quality. The practice of extracting the musk pods from the deer however is very difficult, as they're close to the testicles of the animal, and becomes fatally cruel (a kilo of musk necessitated the loss of between 30 to 50 deer), rendering the practice nowadays extinct. (According to Christopher Brosius however , there are currently ways of extracting it without harming the deer being examined ,which could bring back the practice of using real musk). The precious pods (worth twice their weight in gold) were dried in the sun, on hot stones, or by putting them in hot oil. The resulting black granular "musk grain" is used in alcoholic dilution, called tincture.
Natural musk in its raw state is pungent, with a strong pervasive urinous (ammoniac) smell that borders on the somewhat fecal and needs storage and considerable dilution for it to unfold all its potential. Still, The cultural perception of musk varies significantly, often swayed by the smeller's twisted impression of what they are smelling, as discussed in our Musk Series Part 1. Most common descriptors state animalic, earthy and woody notes or baby's skin scent, yet when perfumers talk about musk they refer to muscone, the very core of the musk essence devoid of the other ingredients that are included in natural musk (such as ammonia, cholesterol and animalic compounds with resinous odoriferous characteristics).
Other Natural Sources of Musk
The matter is further complicated by the reference of musk in relation to other animals from which glandular substastances are exracted: Ondatra zibethicus, the muskrat (ondantra zibethicus) a rodent, the Musk Duck (Biziura lobata), the muskox, the musk shrew, the musk beetle (Aromia moschata), African Civet (Civettictis civetta), the musk turtle, the alligator of Central America, and often people refer to the animalics of civet cats (civettictis civetta) or castoreum from beavers as animals' musk, further confusing the terms (those last two animals produce animal substances that have different odour profiles). Even a particular type of alligator emits a musky secretion, but it proved to be non-functional for this type of odour aim as it is mainly rosy.
Some plants also have musky smelling compounds, usually of a lactonic macrocyclic nature, such as Angelica archangelica (containing 12-methyl-13-tridecanolide and Exaltolide) or Abelmoschus moschatus (ambrette seeds) produce musky smelling macrocyclic lactonic compounds which enrich fragrant compositions and are a handy if expensive resource for niche and natural perfumers. The former is amply explored in Angeliques sous la Pluie by Jean Claude Ellena for F.Malle. The latter is highlighted in Chanel Les Exclusifs No.18 and Musc Nomade by Annick Goutal. Other sources include musk flower (Mimulus moschatus), and muskwood (Olearia argophylla), to a much smaller degree. Even galbanum, a bitter green grass not usually associated with milky sweet musky smells, contains musk components (14-pentadecanolide and 15-hexadecanolide).
Interestingly, animal derived musks are all ketones, while plant-derived musks are large-ringed lactones.
The Rise of Synthetic Musks: History and Classification
Musk deers became a protected endangered species by the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES) in 1979, rendering natural musk almost obsolete in perfumery (The erratic quantities used by a handful of perfumers come from either old stock ~musk only gains in complexity with storage and doesn't lose its aroma for centuries~ or illegal poaching). Therefore all musk used in perfumery today is synthetic apart from only a handful exceptions which are usually small artisanal perfumers (who are often not at liberty to be open about it due to ethical concerns from consumers).
Although "white musk" is a prevalent epithet used as a blanket-term, the reality is somewhat more complex. The high cost and scarcity of natural musk had always been a concern for the fragrance industry and it was a happy accidental discovery when in 1888, Baur discovered the nitromusks. He had actually been working on explosives, hence the "nitro" prefix, when he discovered that the molecules actually smelled nice: the warm, sweet ambience recalled the scent of muscone. The first nitromusk was thus baptized Musk Bauer in honour of this occurence and a frantic exploration of these aromatic molecules started with the aim of replicating the elusive smell of natural musk. Follow-up nitro-musks, notably musk ketone and musk xylene, are rich, expansive-smelling and very warm; they can be savoured in vintage extraits and colognes, notably in Chanel No.5 (at a staggering 10% concentration) where they shine with their come-hither whisper. Later developments effectuated different kinds of musks.
Synthetic musks can be therefore divided into three major classes — aromatic nitro musks, polycyclic musk compounds, and macrocyclic musk compounds. The first two groups have broad uses in industry ranging from cosmetics to detergents but their continuous presence in human tissue and environmental samples coupled with carcinogenic properties has created concern resulting in a ban or reduction of their use in most countries. Macrocyclic musk compounds are generally considered safer and have replaced the nitro-musks (abandonded since the early 80s) and slowly phasing out the polycyclics. For those concerned with the dangers, WWF has an interesting article downloadable as PDF on this link. (primarily against musk ketone, musk xylene ~both nitromusks~ and polycyclics)
Synthetic musks are essential in modern perfumery forming the base note of most perfume formulae.
- Polycyclic musks
However apart from hydrophibic, polycyclics are also lipophilic, as was first discovered in the early 1990s, building up in the bodies of humans and wildlife over time (Daughton 1999).
Traesolide is another synthetic polycyclic musk used as a fragrance ingredient in a variety of consumer products, including soaps, perfumes, and cosmetics and even though Traseolide is not as commonly used as other polycyclics, such as Galaxolide and Tonalide, it has been detected in breast milk, adipose tissue, and blood in humans (Rimkus 1996; TNO 2004; Duedahl-Olesen 2005). They're being steadily replaced by newer molecules.
- Macrocyclic musks
Ethylene brassylate (or Musk T) is a brassilic ester with floral woody facets, commonly used in cosmetics, because it acts as an odour neutraliser to the other chemicals used, as well as in fine fragrance. Notably it is featured in Dove's Cleansing Towelettes, as well as Olay, Cover Girl, Max Factor and The Body Shop foundations.
Globalide (Habanolide) is a metallic smelling, fresh radiant musk: Smell it in Emporio Armani White For Her, coupled with Helvetolide (please see below), where it forms the signature of nose Alberto Morillas in 2001, giving rise to the term "white musk" ~as opposed to the balmy darkness of the prior nitromusks. Or try it in the ultra-popular aldehydic musk Glow by Jennifer Lopez, accenting the fresh white floral components of the formula; the cooly herbal-soapy Cologne by Mugler and the baby-soft"clean" of Clair de Musc by Serge Lutens. It also balances the sweeter calorific elements in Hypnotic Poison by Christian Dior.
Ambrettolide is lightly sweetly-musky, uniquely vegetal with bordeline floral tones possessing exceptional diffusion which comes through from the very top notes through the base of the fragrance! Although it naturally occurs in ambrette seeds (prefered by niche brands or natural perfumers), it is usually synthesized in the lab. Other popular macrocyclics are Thibetolide (Exaltolide) ~more detectable by women than by men~ and Velvione, the latter from "velvet" and "ketone", referencing the velvety softness resembling older nitromusks and famously comprising almost the entirety of Helmut Lang's Velvione cologne formula.
- Alicyclic musks
One interesting case is IFF's Allyl Amyl Glycolate (iso-amyl oxyacetic acid allylester), one of my less prefered musk variants (Chandler Burr describes it as “a combination of the smell of processed pineapple and the tin of the can it comes in”), a clear liquid that can be used in any blend. It possesses sharp green facets with a top resembling the bitter touch of galbanum and a sweet pineapple fruity note. First discovered in 1936, it lagged unnoticed until it was popularised via Italian detergents in the late 1960s. Its use in Camay soap made it familiar and thus it entered fine perfumery: Trace amounts can be found in Alliage by E.Lauder while higher doses can be found in Drakkar Noir by Guy Laroche (1%)and Cool Water by Davidoff (3% which is very high for a powerful synthetic such as this). Trésor, Eternity, and Boss Elements Aqua also use it for its harmonization with the greener notes (lily of the valley, violet leaf).
Newer musks are constantly created, often with imaginative and inspiring names.
Nirvanolide, a chemical produced by Givaudan has a clean sweetly powdery and slightly animalic odour close to the restricted older Musk Ketone. You can smell it in the perfume Forever Elizabeth created by David Apel where it is used in 6.7% concentration. Another chemical with an odour close to Musk Ketone is Muscenone, possessing a very elegant and diffusive musk odour.
Firmenich offers two musk blends, Auratouch 911382 and Auranone 911383. The base of these products contains a captive* musk with a berry top note that performs like a polycyclic musk. Auratouch 911382 is a strong layered musk base with a substantive drydown and contains only triethyl citrate as a solvent. Meanwhile, the base of Auranone 911383—a strong substantive musk base with a delicate floral and somewhat animalic character—has strong ambrette connotations and contains no solvents, or polycyclic or nitro musks.
Meanwhile, the base of Auranone 911383 is a subtle but substantitve assemblage of some of Firmenich's finest musks with ambrette and animalic facets, blended with soft floral notes, devoid of polycyclic or nitro musks. Created around Romandolide, the captive alicyclic is paired with Habanolide, Exaltolide Total, Muscenone and Helvetolide to produce a hard-core musk with traces of sandalwood, amber, violet and powdery notes.
Givaudan has two new synthetic musks: Cosmone and Serenolide. Cosmone, is a single molecule the first C14-macrocyclic musk commercially available, which has a nitro-musk character of great warmth and diffusion which blends well with all kinds of accords. This biodegradable molecule, in addition to Nirvanolide, enlarges Givaudan’s range of environmentally friendly macrocyclic musks and can be smelled in Pi Neo by Givenchy (2008). Serenolide is an elegant white musk with sweet fruity connotations providing warm and soft velvety notes that blend well with all kinds of trendy fruity accords.
Musk R1 (originally from Quest International) is an example of an oxa-macrolide with sensual, powdery musky character.
The fascinating world of musks is far from over: We will return with classifications, descriptions and reviews of musky fragrances on the market!
*Captives are molecules which are patented by companies for their exclusive use for a number of years.
Related reading on Perfume Shrine: Musk Series 1: a Cultural Perception of Musk, Musk Series 3: The Many Permutations of Musk (musk "types")
Rowe, David J. (Ed.); Philip Kraft (2004). "Chapter 7. Aroma Chemicals IV: Musks". Chemistry and Technology of Flavours and Fragrances. Blackwell
Charles (Ed.), Sell; Charles Sell (2005).The Chmistry of Fragrances Chapter 4. Ingredients for the Modern Perfumery Industry". Royal Society of Chemistry Publishing.
Robert R. Calkin and J. Stephen Jellinek, Perfumery Practice & Principles
PChirality & Odour PerceptionJohn C. Leffingwell, Ph.D.
Perfume & Flavorist magazine, Musks in Fragrance Blending
Jenny van Veenen Perfume Making
 Epistola S.Fowler: Musk
Painting Lovers by a Tree Mughal, Muhammad Shah period, about 1725 via lokvani.com. Pics via mikndfully.org, Natural Health Crafters, homotography.blogspot.com