CLSM is an upfront hardcore group from the UK fronted by Jon Doe and Gavin Spong. The group also maintains a label of the same name which has a number of sublabels including G-Core and Clack, on which the majority of their tracks are released. To date the group has contributed dozens of popular vinyl singles to the hardcore scene as well as at least two full CDs—Transmission to Mars and Hardcore Material. Jon Doe and the group are also known for their remixes, displaying the signature style of CLSM.