Mukhallat is not to be confused with attar, which refers to any fragrant essential oil distilled from flowers into a carrier oil (usually sandalwood). So you can have a mukhallat containing attar of roses for instance, but also musk, saffron, oudh, amber (itself a mix)...The variations that distinguish mukhallats are not only the ingredients themselves (i.e. the "recipe") as these tend to tread familiar paths, but also for instance the species of the particular flower used, the origin of an ingredient (such as Omani frankincense versus Somalian), plant or animal based musk, the amber-note recipe, additional oils and the quality and quantity of individual ingredients. It's here important to note that although mukhallat sounds like a mix of all natural essences, in truth this is often not the case.
Oudh/Oud/Aoud (also: agarwood or aloeswood) is one of the most common and confusing ingredients to be featured in Arabian perfumery. Common because there's a significant tradition of using this oleoresin in Middle Eastern rituals, and confusing because so many of the fragrance blends are not based on the natural oud essence for various reasons, as you can see here. Oud/Oudh comes in two commercial forms: den al oudh which is an oil produced via either distilling the wood chips of the Aquilaria tree (a more economical option) or melting a small amount of the resin produced by the tree into a carrier oil. Thus den al oudh can be used neat on the skin as perfume. The pure resin (to be further manipulated for fragrance purposes) is usually referred to as oud mubakhar.
Some of the companies that do quality Arabian-inspired or Arabian perfumery are (in no specific order):
Amouage, Ajmal, Aluwwah.com, Arabian Oud, Al Haramain, ASAQ, Al Rehab, Yas: The Royal House of Perfumes. Rasasi and Swiss Arabian are also credible, if less luxurious.
And of course there are less expensive Arabian fragrant mixes that can be no less beautiful in their own way.