How close did Richard Strauss come to atonality in Elektra?

In his 1909 opera Elektra, Richard Strauss pushed his harmonic language to the furthest extent of his desire toward atonality.1

While the work is characterized by a powerful harmonic idiom and intense, complex overlays of dissonance, Strauss remained a fundamentally tonal composer. The dissonant elements present in Elektra are distinct and separable from the underlying tonal harmonic movement of the score. Unlike the later works of Arnold Schoenberg, where tonality was abandoned entirely, Strauss’s approach in Elektra utilized extreme dissonance to convey psychological obsession and intense emotion without fully relinquishing the structural foundations of the tonal system.231