Toddlers Marimba Elite is a great music app.
The marimba is a percussion instrument consisting of a set of wooden bars struck with mallets to produce musical tones. Resonators suspended underneath the bars amplify their sound. The bars of a chromatic marimba are arranged like the keys of a piano, with the groups of 2 and 3 accidentals raised vertically, overlapping the natural bars to aid the performer both visually and physically. This instrument is a type of idiophone, but with a more resonant and lower-pitched tessitura than the xylophone.
The marimba was developed in Central America by African slaves, and descended from its ancestral balafon instrument, which was also built by African slaves. Marimba is now the national instrument of Guatemala and Costa Rica.

Recent changes:
The first version.