Facing Parque Marimba [1], Museo de la Marimba (9 Calle Pte. Nte. at Av Central Pte, 9 a.m.–2 p.m. and 4–6 p.m. Tues.–Fri., 9 a.m.–noon Sat., US$2) is a small but well-organized museum with interesting displays on the origin, evolution, and cultural significance of marimbas, including touch-screen exhibits where you can see and hear recordings of famous musicians and performances.
It also has a large collection of instruments, from simple to spectacular marimbas, and you can peek in on students taking marimba lessons in the attached classroom. The admission price is a bit high for the size of the museum, but it’s a worthwhile stop nonetheless.
Links:
[1] http://www.moon.com/destinations/chiapas/tuxtla-gutierrez/sights/parque-marimba