As a percussionist I must point out for the benefit of those who do not or have limited knowledge of melodic percussion instruments. This is a small typo I found on pages 46 & 47 with the labeling of Marimba and Xylophone. On page 46, is a picture of a Marimba that looks to be at least 4 octave, not a xylophone as labeled. On page 47, that is a picture of a wood (usually rosewood) xylophone usually no more than an octave or two, not a Marimba.
This is just a small mislabeling of these instruments however I feel strongly one should take note of the differences. Glockenspiel and Vibraphone are fine.
By the way, the Marimba is capable of longer sustaining notes due to the longer resonators and lower register of the instrument.
I used to own a Musser Concert Grand Marimba and it always twisted my nerves when someone would come up to me and ask, where did you get that Xylophone?