About the sheet music:

Matt Springer's mallet percussion ensemble arrangement of the three pieces by Grieg was originally published by C.P.P./Belwin (later Warner Bros.) in 1996, and now has been re-released as a 2nd Edition (2008) through Khach-22.  These arrangements are very well suited for this mallet percussion ensemble instrumentation, consisting of four players using orchestra bells, xylophone, marimba (4-1/2 octave low F), vibraphone, and triangle.  A 4-1/3 octave low A marimba can be used if necessary, but it is more effective with a low F instrument.  Having two sets of orchestra bells makes it easier to play, but it can be done with two players on one instrument.  This ensemble is rated for advanced high-school players and up.

The original Belwin edition is currently still available from various sources.  The Steve Weiss Percussion catalog carries the new Khach-22 edition (search for Springer).

More details, including program notes, reviews, history, and streaming audio of each movement

For non-percussionists:  What are these instruments?

You don't understand the new cover design?