What today is called Progressive Thrash Metal was the thing that was called Techno-Thrash back then in the 80s...so it doesn't have anything to do with Techno or Tekkno. Prominent bands of this style were WATCHTOWER, MEKONG DELTA, CORONER or HEXENHAUS. An insider tip of this style is the second album of WRATH from Chicago, produced by Ronnie Montrose.
Their debut “Fit Of Anger“ was just mediocre US-Metal with shrill vocals, done by Gary Gollwitzer, who had a really mean organ. Actually you could relate this music to the Bay Area Thrash, because the riffs and speed sound exactly like what made EXODUS, FORBIDDEN or DEATH ANGEL so popular. In the case of WRATH many breaks were added, but these felt so conclusive that basically no fan should have problems with “Nothing To Fear“. But there are still these really grumpy vocals...Anyways, WRATH were great, the album a masterpiece and the vocals became a trademark! Unfortunately Gary didn't sing on the next WRATH album and he changed his vocal style completely with his follow-up bands STYGIAN and UNLEASHED POWER.
The screeching was replaced by monotonous, deep 08/15 singing...so it's not surprising that the mentioned bands never really drew attention. At least WRATH is popular in the underground! (Online June 2, 2004)