Symphonic join of maps between the spheres

In the previous papers Nakauchi and Takenaka (2011) and Kawai and Nakauchi (2011), the first author introduced a stationary map for the functional of L2-norm of pullbacks of metrics. We call it a symphonic map. In this paper using the argument of Xu and Yang (1993) (see also Smith (1975) and Ding (1988)), we give a notion of the symphonic join of two symphonic maps between the standard spheres.