It´s fairly new, has a 42 degree sponge and I think it could be seen as a modern successor to Calibra Sound.
Not a high performance rubber but for "controlled" offensive with an emphasis on spin (so I read...).
It could be a soft version of the Mantra Pro, which they´ve released as XH, H and M so far, so an S version would be kinda logical, but maybe SOUND in the name makes for better associations ;-)
There´s also a rubber aimed at beginners called Mantra Control. That is obviously reduced in power (entry level "tensor"), has a 45 degree sponge and might rival Vega Intro or Hexer Duro or whatever else is given to learners.