If the xylophone is the upper or soprano instrument of the wooden keyed pitched percussion section, then it’s lower relation is the marimba. Unlike the more brittle quality of the xylophone, the marimba is softer, and less penetrative in tone. It’s played with soft mallets usually made of yarn, and it’s tone can be quickly covered by other instruments, so the composer should take care to keep the accompaniment thin, and soft, when writing for the marimba. With it’s gentle nature, and lack of power or bite, the marimba is less often seen in arrangements than the xylophone, but still offers a warmer sound colour than the xylophone when used well. The unique tone of the marimba is a surprising, and often pleasing sound colour in an arrangement, no matter how little it’s used. Writing mallet rolls for marimba is a safer proposition than for xylophone, as the performer will roll by default any note longer than a crotchet, or quarter note, unless otherwise specified in the score. (and it would make no sense at all for the composer to write minims, or half notes, for the marimba player, and indicate he’s not to roll the note.)
Like the xylophone, the marimba player can use up to 4 mallets to play, but care should be taken that the requirement for multi mallets is for chordal work, and not musical lines or phrases that required rapid pitch changes over the keyboard. It’s also consider poor writing to mix chords and more adventurous melodic lines at the same time, unless scored for 2 marimbas, giving each a defined role.