The third of five movements of a "Sinfonia concertante" in an expressionist / late romantic idiom for string orchestra. A scherzo in a modified rounded binary form, contrasting an ecstatic (Scriabinesque?) outer section thematic complex with an esoteric (and arguably Eastern-inflected) inner section thematic complex, though elements of sonata-allegro form are present. Note the resurgence of the whole-tone passage from the "Capriccio tenebroso" first movement, in the inner section's development. Toward the end the movement builds up to a sparkling climax, an ascending "super-Lydian" figure over an increasingly dissonant pedal giving way to a thickly adorned "extended tonic" chord [I add2 add6]. 

You may find the engraved "conductor's score" here.    

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