Look deeper into the music. Therion's music is heavy-metal riffs with choirs and orchestras on top.
Most people's problem with Therion is the marriage of these two styles. The feeling is that they don't belong, and that they're separate. Such is suggested by saying Christofer Johnsson simply writes some metal riffs and throws some strings and horns in to fill in the spaces. That would be accurate for, say, Metallica's little symphony effort. When I listen to a Therion song, I hear one piece of music, period. If you choose to separate it in your mind, well, that's your prerogative.
Orchestra and classical are not synonyms. Classical music is conceived as constantly developing music, almost bordering on absolute in its possibilities, and where every sound (or you can say "note") is crucial and important to the experience.
I didn't say it
was classical, just classically influenced. The word classical refers to a style, or a region of the musical landscape thus explored, if you will. The word orchestral refers to the method of delivery of the music. It's delivered through an orchestra. I don't sit and listen to "Via Nocturna" and expect it to sound like Frank Zappa's "The Girl In the Magnesium Dress" (which is the ideal piece, if we go by your definition of classical music.) Classical is a very broad term, as it can refer to symphonies, sonatas, fugues, concertos, minuets, marches, operas (various forms, such a singspiels), requiems, string quartets, even chanting, etc. What these forms all have in common, is their origin. They were all born out of the classical period in Europe. That's why the definition of the word has those parameters in the western world, as it doesnt include the traditional classical music of places like Mali, China, Indonesia, India, etc.
Metal music (which includes Therion and Lacrimosa), when you go to the root of it, is basically about repeating riffs on distorted guitar. "Open-minded" bands may replace or complement distorted guitar with other sounds, but the core of the music stays the same. The orchestra is just a decoration in the case of the bands mentioned here, and especially Therion.
This may have been true at one time, but there is a lot "metal" music conceived today that is as complex and constantly developing, as you put it, as conventional classical music. The music of Nile, then, is just as much classical music as the works of Mozart and Stravinsky. Furthermore, many styles of jazz can be considered classical if we adhere to your criteria. Somehow, I doubt you've listened to much Lacrimosa, because, as I mentioned in my earlier post, they have quite a few pieces that are completely classical. Should a group that plays pure classical as well as classical/rock/metal integration be considered a metal band? To be honest I don't care. Labels are the least of importance. . .
You know, I'm listening to Haggard now, I hear little repetition, yes even in the metal riffs that come in some times. Of course, there IS repetition in classical music, as a piece's theme surfaces time and time again; though of course it's manipulated as the piece progresses. I love both metal and classical forms of music, as the partitions have been erected. But in the end, music is music. Therion is music. Music I consider brilliant, complex, and endearing. They don't "suck," as you put it. If you really believe that, you either have very restricted musical taste, or you're not thinking clearly, because when you say they suck, you're saying that everything about their music is a failure. If that is what you truly believe, then you have only my pity.
I'm not looking for an argument. I just want you to see that there are many ways of perceiving the world. Our conception of the universe comes purely through our senses. Each individual is different, and by being open to the endless ways of interpreting reality, a person can assuredly find bliss in every moment of their life. Many human definitions and concepts are abstract, music being one of them. I don't go around to caves in France, critiquing the style of ten thousand year old paintings. Such an excursion would be to admire the way someone has expressed their conception of their own known world. Give that some thought. And D Mullholand, I wish you the best of luck on your own composing. I hope one day you'll share with us your own beautiful interpretation of the world. I'm quite confident that it won't "suck."