Bar

The musical bar is any hard, solid substance used to produce a soundwave. Due to the density of the material of which the bar is made, the sound is much louder than that of a string without a soundbox. Bars thus generally do not require soundboxes. A bar instrument may consist of a single bar (such as the wooden bar, called claves), or a series of bars of different lengths to create different pitches (such as the xylophone or marimba). Musical bars are made of many different types of materials: wood, metal, plastics.

A membrane musical instrument may be regarded as a relatively tin bar, or bar with larger dimensions along breadth and width axes. Bars are typically tensed either naturally (such as a piece of wood) or during the manufacturing process (such as tubular bells), while membranes usually allow some tension be applied by the musician (eg. tunable drum vellums).

Bars could be struck (such as the xylophone), rubbed (Tibetan singing bowl, which could also be struck, or cymbals and glass rubbing), or bowed (such as the musical saw, which might rather be regarded as a membrane instrument, and the glass harmonica).

Claves

Source:
http://blog.timesunion.com/griggs-janower/files/2011/10/claves-Rose78DP174.jpg

Wood blocks

Source:
http://www.sonor.com/pbas/sonor_fe/sonor/english/kategorie.html?a-quicklink-n_katid=171

Soundclip

http://www.youtube.com/watch?v=ra0z59GH4n0
http://www.youtube.com/watch?v=Rgc839e_wVc