Glenmorangie Signet is very different from any of its stablemates; in fact, very different from any Highland malt I've ever tasted. Some of its barley is roasted chocolate malt, which apparently gives a nutty, coffee-like aroma (which you certainly get with this one!) Some of the spirit comes from Oloroso sherry butts, and much of it is finished in charred new white American oak. There are also whiskies in here that are 35-40 years old (hence the high price tag). This sample comes to me from @misslauren - it's been open for a couple of years.
The colour is a deep, almost reddish gold. The rich aroma is very unusual: dark chocolate, roasted walnuts, blood orange, buttered dark rye toast! Roasted coffee beans (but doesn't quite smell like coffee...) Dark dried fruits such as dates and raisins. Has an dark rum quality to it. Fascinating, but I found water brings out a sulphurous note.
Quite meaty on the palate, with baking spices, oak and black liquorice. Very nutty - walnuts and roasted almonds - and very citrusy too, with more blood orange and lime zest. Very complex but a bit of a mishmash of flavours going on here; water helps, though, by bringing out more spices (chili, paprika).
The finish has quite a bit of wood to it, with bitter chocolate and more lime. I remember liking this more than I do now - not to imply that it's not good whisky, it certainly is - but this used to be my favourite Glenmorangie. Tasting it next to the Nectar D'Or though, it doesn't quite hold up - huge complexity but many of the notes clash together, and it is a bit sulphurous. Winner of Best Highland Single Malt at the 2011 World Whiskies Awards.
@talexander, I think that both of your experiences with Signet are quite valid. I find that Signet is hugely different depending upon its air exposure. There is a period after a bottle is open for awhile during which it is lush and juicy. Before that it's rather locked up. Afterward it goes more dry, austere, and bitter. During the lush period the bitterness is well-balanced and the effect is quite beautiful.
Thank you - good to know my memories of it may have some validity!