The opera is noted for its numerous expansions of harmonic practice; for instance, one significant innovation is the frequent use of two consecutive chords containing tritones (diminished fifth or augmented fourth), neither of which is a diminished seventh chord (F–B, bar 2; E–A-sharp, bar 3). "Tristan und Isolde" is also notable for its use of harmonic suspension – a device used by a composer to create musical tension by exposing the listener to a series of prolonged unfinished cadences, thereby inspiring a desire and expectation on the part of the listener for musical resolution. While suspension is a common compositional device (in use since before the Renaissance), Wagner was one of the first composers to employ harmonic suspension over the course of an entire work. The cadences first introduced in the prelude are not resolved until the finale of act 3, and, on a number of occasions throughout the opera, Wagner primes the audience for a musical climax with a series of chords building in tension – only to deliberately defer the anticipated resolution. One particular example of this technique occurs at the end of the love duet in act 2 ("Wie sie fassen, wie sie lassen...") where Tristan and Isolde gradually build up to a musical climax, only to have the expected resolution destroyed by the dissonant interruption of Kurwenal ("Rette Dich, Tristan!"). The deferred resolution is frequently interpreted as symbolising both physical sexual release and spiritual release via suicide - the long-awaited completion of this cadence series arrives only in the final "Liebestod" ("Love-Death"), during which the musical resolution (at "In des Welt-Atems wehendem All") coincides with the moment of Isolde's death.