Any electronic source — dedicated hardware or an app — that loops a lehra in a chosen taal and key, standing in for a live melodic accompanist during practice. The machine's virtue is inhuman steadiness: it never follows you, which is exactly the discipline solo practice needs.
Treat it as a fixed wall to play against — layakari, tihais, and full solo arcs all get verified against its unwavering cycle. Tabla Focus's Lehra feature plays that role.