If you could step behind the back wall of the stage of Avery Fisher Hall, you would find yourself in the Percussion Room. Slide whistles are scattered on a table and chunks of wood are stacked on top of the closets that line the walls. Five huge timpani crowd a narrow hallway.

The three-member percussion section — Principal Christopher S. Lamb, Associate Principal Daniel Druckman, and Joseph Pereira — and Principal Timpanist Markus Rhoten soon come in. One of them opens a closet, revealing rows of mallets, drum sticks, shakers, hand drums, and bells: a treasure trove of sound producers. It is March, and the musicians have just rehearsed György Ligeti's Violin Concerto, a late 20th-century piece that showcases the section's virtuosity and elegant precision. Says Mr. Lamb, the senior member of the group, with 22 years in the Orchestra: "It has us bowing cymbals, playing slide whistles, and playing in unison on xylophone with the soloist. This kind of piece shows all the ways we participate in the orchestra on a grand scale."

It was not always thus. It was only in Beethoven's time that timpani (also known as kettle drums) became a regular feature of the orchestra. Since then, that core instrument has been evolving. "In Wagner's period," explains Mr. Rhoten, who is in his first season with the New York Philharmonic, "a pedal system was developed so you could tune the timpani faster and play more notes. Wagner, Strauss, and Mahler took advantage of that, and the instrument has constantly improved to have a greater range."

At around the same time, composers began calling for an ever-widening battery of percussion instruments. "Beethoven didn't write for slide whistle," says Mr. Pereira, the Assistant Principal Timpanist as well as section percussionist, "but today's composers are always looking for new sounds."

And "new" can mean anything from cowbells and chimes to brake drums, typewriters, and 65-gallon drums filled with water. Earlier this season, for example, the orchestra gave the world premieres of two New York Philharmonic commissions, by Esa-Pekka Salonen and Melinda Wagner; both called for timpani plus dozens of other instruments, including tom-toms, tam-tam (a Chinese gong), and an array of bells and shakers, many of which, Mr. Pereira points out, are borrowings from other cultures.

The musicians clearly enjoy the variety. "Part of our preparation," says Mr. Druckman, who, like Mr. Pereira, is a composer, "is figuring out which instruments or mallets or sticks to use. In terms of color, these are big considerations."

Sometimes they have to invent instruments to achieve a desired sound. Mr. Druckman, who joined the Orchestra in 1991, recently showed a visitor one of his creations, a slide whistle with a school ruler attached to indicate pitches. "When composers can't figure out who should play something, we're the default," he says. "If somebody wants something unusual," Mr. Lamb adds, "they come to us."

The closing months of the 2006-07 subscription season typify the section's versatility. There are four works by Brahms that include great writing for timpani, and Bartók's Concerto for Orchestra, with an exposed solo for snare drum for Mr. Lamb. The subscription season's finale is Mahler's Seventh Symphony, which calls for an expanded section of eight percussionists to play timpani and a colorful assortment of cymbals, chimes, tambourine, and bells.

These players revere their predecessors at the New York Philharmonic — Arnold Lang, Walter Rosenberg, Buster Bailey, Sol Goodman, and Roland Kohloff — who were their teachers and mentors. "Their personalities and philosophy still resonate within the section," says Mr. Lamb. "Buster Bailey liked to say that percussion is the spice of the orchestra. There are times when you need a lot of spice, and there are others when you need just a touch. I don't think you could call any other section the spice of the orchestra."

Stephanie Stein Crease is a music journalist and author; her book Gil Evans: Out of the Cool won the ASCAP-Deems Taylor Award.