The BLM is a button grid control surface with LED feedback that can be used as a controller for the MIDIbox SEQ V4, as well as for the SEQ V4L. The full-size BLM (the “16×16+X”) has a 16×16 button grid, with extra control buttons along the sides. Larger or smaller BLMs are possible - the BLM protocol scales to accommodate different button matrix sizes.
There are many BLM options available. You can build a hardware BLM - some users have designed PCBs, others have used veroboard. Ilmenator has created a 16x4 hardware BLM. A Lemur application is available that provides a virtual BLM on an iPad. BLM emulation software is available for Linux, Windows, and Mac computers. The Lemur app and the emulator software can be downloaded on this page.