When Roopa Kalyanaraman Marcello, a classical music aficionado in Brooklyn, asked her Amazon Echo for some music recently, she had a specific request: the third movement of Beethoven’s “Emperor” Concerto.

“It kind of energizes me, motivates me to get things done,” she said.

But the Echo, a voice-activated speaker, could not find what she wanted. First it gave her the concerto’s opening movement; then, on another try, came the second movement. But not the third.

Exasperated, Ms. Kalyanaraman Marcello gave up.

“Just play something else!” she recalled saying.

Her frustration may be familiar to fans of classical music in the streaming age. The algorithms of Spotify, Apple and Amazon are carefully engineered to steer listeners to pop hits, and Schubert and Puccini can get lost in the metadata.

Classical music has always been a specialized corner of the music business, with a discerning clientele and few genuine blockbusters. But by some measures the genre has suffered in the shift to streaming. While 2.5 percent of album sales in the United States are classical music, it accounts for less than 1 percent of total streams, according to Alpha Data, a tracking service.