I thought it might be helpful to list some of the aroma chemicals that I find most useful, most often, in no particular order: Synthetic Ambergris - there are several and I use one in many, many accords I make Iso E Super - adds a unique diffusive quality to many accords. IFRA limits this to 20% but that's more than you are ever likely to want to use anyway - I find 2% is plenty in a finished product (that's 2% of the total product not 2% of the aromatics, just to be clear) Hedione - works well in lots of blends especially florals, it brightens the blend and enhances many florals especially the jasmines, but by no means only those. It can be used quite freely. Synthetic Civet and Castoreum - these are vital for adding animalic notes to perfumes where you are not using real animal ingredients. Use with caution and keep well diluted - 0.1% and 1%. Ambrarome is a less powerful animalic note with more leathery quality than civet that works really well to fix and diffuse florals especially chypre types. Musks: Ambrettolide, Exaltolide, Galaxolide, Ethylene brassylate - all useful, all slightly different. Vanillin, Ethyl vanillin - these are vital for sweetening and softening blends - strong chemicals though so keep diluted to about 1% Lilial, Lyral and hydroxycitronellal - these are all imitations of Lily of the Valley, all different and all restricted by IFRA to low usage. Even so they enhance a lot of floral and other blends in small amounts and are lovely used in combination with each-other and many florals. Methyl ionone (alpha) - useful to add some 'punch' to florals and add depth - quite heady and not that nice on its own but enhances a lot of blends. Geranyl acetate and Linalyl acetate are especially useful to add top notes when you don't want either citrus or lavender to be apparent in your blend. They will enhance all sorts of other things too. Calone is a wonderful clean, fresh sea-breeze note that is essential for creating those popular 'aqua' type colognes. Strong stuff so dilute to 1% Floralozone is similar but more versatile in small quantities in lots of florals to brighten them up. Helional, verdilyn and cis-3-hexanyl acetate are all good green notes Javanol is a good replacement for or booster with sandalwood Cedramber is a nice cedar-wood like scent with some depth Veramoss is a substitute for Oakmoss - not as good as the real thing but handy to boost it because the IFRA permitted quantities are so low.
There are loads more, but those are probably the ones I use most often at the moment. I'm always experimenting with different ones . . .