Swiss critic William Ritter recalled Mahler explaining his use of cowbells: "When I put cowbells in my orchestra it's to create that feeling of height, of solitude, of silence." Here they are in a passage from the Seventh Symphony.

In the second “Night Music” of the Seventh Symphony, Mahler brings mandolin and guitar into the ensemble, marrying the unmistakable sound of a lover’s serenade to the symphony orchestra. Like sparkles of moonlight on a dark surface, these plucked sounds stand out against the otherwise dark colors employed in this movement.

In his setting of Friedrich Rückert's "Do Not Look into My Songs" (Blicke mir nicht in die Lieder), the accompaniment imitates the buzzing of bees, as a constant musical metaphor for the dedication and perfectionism of the artist.

This cinematic passage from the second movement of the Seventh Symphony starts with a passage of woodwind solos, built from stylized versions of bird calls. Imagine how the approach of the night watch (in tuba and bassoon) agitates a flock of birds at night: they noisily take flight and scatter; then all is quiet again.

After the premiere of his First Symphony, Mahler found that the opening “sounded far too substantial for the shimmering and glimmering of the air that I had in mind.” So he changed the instrumentation to the whispery sound of string harmonics. He continued revising the instrumentation for five more years before the symphony’s publication.

Mahler underscored the importance of tone color to aesthetic impact when he wrote about the Funeral March of his First Symphony: “In the March movement the instruments are disguised and go round dressed as strangers. Everything has to sound deadened and muffled, as if ghosts were parading past us. Making sure that each new entry of the canon theme comes over distinctly, with a surprising tone color that attracts attention, caused me a real headache! Eventually I got the instrumentation right, resulting in that weird, otherworldly effect you noticed today. And I don’t think anyone has yet managed to work out how I achieve it.”

Mahler’s non-traditional approach to traditional instruments gives them new roles. He takes the squeaky E-flat clarinet, so familiar to him from military bands of his childhood, and makes it the cheeky leader of a dance band — in the slow movement of a symphony!

Later in his life, like Berlioz and Brahms before him, Mahler turned to the sombre-hued viola for his most personal confessions. The violas open the Tenth Symphony with fifteen gentle bars that hint at a possible G major harmony; but as they progress, they seem to repudiate the idea of resolving into in any key at all. At the last possible moment the strings envelop them with a warm F-sharp major embrace.