Musk was originally obtained from animal sources, although that is no longer the methodology. However, when this technique was used, the anal glands of the musk deer and civet cat were extracted to retrieve this scent. Musk is now produced synthetically.
White musk smells soapy and clean with a bit of floral nuance and something of a bite to it. It is used in detergents and fabric softeners as well as in perfumes. White musk can be strong, although it may smell restrained while in a bottle. Use it sparingly.
Egyptian musk is a variation of a musk blend. In this musk, the clean, scrubbed skin hint is the dominant part. This musk is more discreet than white musk. It is often combined with patchouli and sometimes rose petals. Egyptian musk is so delicate that its fragrance would never offend someone who is sensitive to perfumes.
Egyptian musk has a long and fascinating history. It is said that Cleopatra wore it and this is what helped her win over Mark Antony. The late Carolyn Bessette-Kennedy was known for wearing Egyptian musk oil, which, on her, was described as intoxicating, earthy and heady. Egyptian musk oil does contain patchouli, which some people don't like the smell of, but it is not overpowering and blends well with the other ingredients.
Musk is usually a base note in perfume. A base note is the main theme of the perfume along with the middle notes. The base note is what gives the perfume its solidity and depth, achieved by boosting and holding together the strength of the middle notes and the top notes that are lighter. The base note is historically rich and profound. You don't normally smell the base note until the perfume has been on you for a half an hour. Musk base notes are often still detectable a day later. Musk is long-lasting so it is a good fixative for perfume.