The MD421 was developed 20 years ago and continues as one of their most popular models. The frequency response is switch selectable to provide a flat response or one that rises above 3kHz to provide maximum intelligibility. Originally intended for Radio and TV interviews, the 421 is now mainly used for bass drum, bass guitar, double bass, woodwind and brass. This model cannot be overloaded which explains why it is often found inside bass drums. It includes an effective pop and blast filter.