Arguably the most forward-thinking jazz artist of his generation, Los Angeles saxophonist and composer Kamasi Washington has never hesitated to step outside his comfort zone. He’s logged studio time with Kendrick Lamar and St. Vincent, and performed onstage with Lauryn Hill and Snoop Dogg. But he’s most famous as the visionary bandleader behind sprawling albums like “The Epic” and “Heaven and Earth,” where song lengths routinely stretch beyond 10 minutes, and nearly three-hour runtimes are standard issue. So it required a massive change of focus for him to craft the score to Nadia Hallgren’s Michelle Obama documentary “Becoming” (Netflix), composing and performing miniature jazz suites whose brevity proves no obstacle to Washington’s typical musical adventurousness. It seems the effort was worth it: he is nominated for an Emmy in the docuseries or special music composition category.