Percussion
We can infer from the scale of the art, and from the existence of what may have been a viewing gallery at the far end of the cave complex (the Belvedere Gallery), that the subject matter of the Chauvet Cave was deemed to be important. A visit to the cave was therefore probably accompanied by sound.
In the Gallery of the Red Panels, which would have been near the beginning of the visit (image above), we see two gǔn 丨, meaning to strike, adjacent to two pictographs that may be different sizes of a percussion instrument. I haven’t been able to find a musical instrument to match the image. However, the character zhōng 中 is a similar shape. Zhōng can mean to be struck. Hence we may have two lines indicating downward movement, and two things to be struck. I think that it may be an instruction to use percussion sounds at that point in the visit.
Author's Note
According to Mr Clottes, the drawings are found on a large rock that hangs down from the ceiling¹. It may be that the rock itself is meant to be struck. However, my understanding is that there is plenty of space near the rock pendant for musicians. Moreover, a short distance away is a pile of rocks. Could the pile of rocks be stone chimes?
References
Image Credit: Traits verticaux et figures indéterminées sur un pendant rocheux: Photo: Jean Clottes: Courtesy, Jean Clottes
Note: 1. Jean Clottes, 2008: Cave Art: Phaidon Press Limited, p.33