Anton Webern (1883–1945), Five Orchestral Pieces (1913)
The whole piece — it is all of six measures long — can be shown on one line of music:
Webern, Five Orchestral Pieces, Op. 10. © 1923 by Universal Edition A.G., Vienna. Copyright © Renewed. All rights reserved. Used by permission of European American Music Distributors LLC, U.S. and Canadian agent for Universal Edition A.G., Vienna.
Listen to it several times: The music feels exceptionally concentrated because the relationship between the notes is so strained by the “atomized” orchestration and the complex network of pitches and rhythms. Each note somehow becomes a separate little source of tremendous energy. This might be described as a very short time segment of very high intensity.