Instruments that have bars and are played with mallets comprise the family known as mallet instruments (AKA barred instruments or pitched percussion). At the present time, Music House uses two of these – xylophones (wooden keys) and glockenspiels (metal keys). These particular instruments are called “Orff instruments” because they feature removable keys. Thus the notes can be arranged in different combinations and patterns, encouraging exploration of various scales and modes.
These instruments are used primarily as melody instruments with an alternative tone color to the piano. It is possible to orchestrate a tune by assigning different phrases to different mallet instruments, providing a drumbeat or other percussion and thus transforming a song. Mallet instruments also lend themselves to the exploration of tonal relationships and intervals. Even chords are possible if you can manage 3 mallets at once (or invite a friend). If you really want to have fun with this, go to Jim Doble’s Elemental Design site and try some of his unusual mallet instruments online.