4 Real Communication was a short-lived trance label, set up by David Gates and Malcolm Stanners, mostly known as Salt Tank. Unfortunately, the lifespan of the label was limited, as per the output of Salt Tank...
Additive was a sublabel of EMI, focused on progressive trance music. Under the label, several known artists of the genre were introduced to the masses, such as Chris Cowie (X-Cabs), Oliver Huntemann (Kay Cee), Ralph-Armand Beck (Taucher) and Laurent Véronnez (Velvet Girl). The declined popularity of trance in the mid-00's led to the closure of the label.
Armind is a Dutch trance label, which was the first imprint of Armada Music, the colossal EDM label. It was founded by Armin Van Buuren (prior to his superstar DJ status) and serves as home of his all own productions. While the current output of Armind and Armada Music in general does not seem inspirational, the very first releases were instant classics (Alibi - Eternity, Rising Star - Touch Me, Motorcycle - As The Rush Comes).
Audio Therapy was a label run by Dave Seaman, from 2000 until 2010, specialized in progressive house. It was the first production home of Stelios Vassiloudis, one of my favorite Greek artists of the genre. Additionally, the progressive breaks classic Habersham & Phil K - Cloudbrake can be found in the label.
Avatar Records was founded in 1997 by Israelis Avichay Avigal and Peter Eibenschutz. The label is mostly popular for its psy-trance output, massively produced in Israel. I am not very familiar with the genre, it is worth mentioning that the label hosted the first studio album of Astropilot (Fruits Of The Imagination), a solid release.
