Provision of controlled primary frequency support to asynchronous AC areas through an MTDC grid using a minimal-communication scheme is proposed. Under nominal operating condition, only voltage droop is considered to allow the AC systems operate asynchronously as they are meant to. When an AC system needs support, the corresponding converter transmits basic information via a distress signal through the existing DC lines or through existing communication channels used for common DC voltage-droop control. For AC disturbances, the frequency droop is activated with values that are predesigned based on the proposed design procedure. For converter outage, power references are modified in such a way that the DC power redistribution does not or minimally affect the AC-side frequencies. Simulation studies showing the effectiveness of the proposed strategies are presented.