Another instrument, but one which can hardly be called musical, is the bamboo horn used for signaling and calling purposes. It consists of an internode of bamboo with one partition wall removed. An opening large enough for the mouth is made on the side of the bamboo near the other node. In using it the mouth is applied to this aperture and a good pair of lungs can produce a loud booming blast. After the occurrence of a death, especially if the deceased has been slain, it is customary to use this instrument as a means of announcing the death to near-by settlements, thereby putting them on their guard against any of the slain one's relatives who might be impelled to take immediate vengeance on the first human being he met.
SOUNDERS
A method of signaling, much in use among the mixed Manóbo-Mañgguáñgans of the upper Agúsan, consists in beating on the butresses[sic]23 of trees. It is surprising how far the resultant sound travels in the silence and solitude of the forest.
23Da-líd.
In connection with musical instruments it may not be out of place to mention the bamboo sounders24 attached to looms. They are internodes of bamboo with apertures in the joint wall and a longitudinal slit extending almost from node to node. One of these always constitutes the yarn beam of the loom.
24Ka-gú.
These internodes, besides serving to support the fabric during the process of weaving, denote by their resonance that the weaver is busy at work. The movement of the batten in driving home the weft produces a sound that, owing to the resonance of the bamboo yarn beam may be heard for several hundred meters.
When the Manóbo maiden is especially desirous of calling attention 'to her assiduity and perseverance, she has an extra internode placed in an upright position against the yarn beam just described. This doubles the volume of sound and serves to intimate to visiting young men that she would be an industrious wife.