The origins of the Marimba
What is the difference between the marimba and the xylophone?

Both the marimba and the narrowly defined xylophone are xylophone instruments, and they look virtually identical. If you want to find out which kind of xylophone instrument a given unit is, you should look at the undersides of the tone plates for the lower-ranged notes. The central portions of these bars on a marimba are considerably hollowed out, while those of a xylophone are wavy. Comparing the sounds, the marimba has a soft and mellow tone that sounds like it could meld with wind instruments. The impression one receives is somewhat restrained. By contrast, the xylophone's notes could be described as distinct and sharply defined.

Example of a marimba performance

Example of a xylophone performance

The marimba has soft tones, and the xylophone has hard tones. This difference is the result of each instrument's tuning method. The marimba is tuned on even-numbered harmonics, with tuning on the fundamental pitch, the fourth harmonic, and the 10th harmonic. The xylophone, however, is tuned on the fundamental pitch and the odd-numbered third harmonic. Tuning the same C tone plate, on the marimba, the bar is matched to C, high C, and high E; on the xylophone, the bar is matched to C and high G. When the marimba, whose harmonics resemble those of woodwind and string instruments, is played with an orchestra, the notes blend in. The reason that the xylophone's notes stand out is that the tuning method is different.
*Yamaha's xylophones are tuned with odd-numbered harmonics, but some manufacturers make instruments tuned with even-numbered harmonics.

Example of the tuning