PLIFFERS 1 & 2
These plastic rods are sounded by stroking with rosined fingers or high traction gloves to excite longitudinal vibrations in the rods. This pattern of vibration, with wave fronts reflecting back and forth lengthwise in the material, is similar to the patterns in wind instrument air columns, and people sometimes comment that the pliffers sound like a recorder. Waves travel faster in solid materials than in air, so the rods must be longer than the equivalent air column would be to produce the same note. Plastic was chosen as the material because harder materials such as metal would require even longer rods. (See, for instance, the instrument called Dansal 3.)
A video of this instrument can be found among the demonstrations in this youtube playlist.