This new useful it was designed and patented by Afonso Castro
The main function is to avoid that the drones begin to be heard before the chanter and that they don't be heard after stopping.
Besides the sound of the drones is more stable and where more perceives is in the Trace back of octaba , because it diminishes a lot the variations of these.
Of simple placing is very easy to regulate, with a simple twist with the key, achieve to regulate it so that it begin and finalise to the pair of the chanter.
It serves for all type of drones, of cane or synthetic and can use so much for the bass drone, tenor drone and high drone
Sight of the valve in several positions
The valve enters and regulated in the interior of the drone stock, with the key of drone that also supply we. The key has on the one hand thread, with which threaded the screw of the valve and like this can enter it or withdraw it of the drone stock. On the other hand it has hexagonal head, with which regulate in the valvula to that presion begins to sound the drone
Key of the valve of drone
In the following image can see the valve in the drone stock