This past June, Ibragimova, 29, released a recording of Ysaÿe's six violin sonatas, known as some of the most treacherous solo works in the repertoire. They are portraits, of a sort, of six violinists whom the composer knew in the 1920s: Joseph Szigeti, Jacques Thibaud, Georges Enescu, Fritz Kreisler, Mathieu Crickboom and Manual Quiroga. "You hear the personalities," said Ibragimova. "They feel like proper little dedications."

Ibragimova arrived at the station early one August morning after having performed a late-night (10 pm) recital at Lincoln Center's Kaplan Penthouse—one of at least two such performances this summer, another being at London's Royal Albert Hall in July. The violinist believes the late shift helps put audiences in a more contemplative mindset for listening. "I think the atmosphere changes for the time of day," she said. "People listen differently."

For her second performance, Ibragimova offered the Largo from J.S. Bach's Solo Violin Sonata No. 3.

Ibragimova's still-young career is notable for the sheer breadth of her repertoire interests. She has also formed an all-female string quartet called Chiaroscuro that uses period instruments, though she herself opts for an unorthodox approach to equipment, changing strings, pitch and bows on her (comparably modern) 1780 Anselmo Bellosio violin. "Whilst it works, I find it's not ideal," she said. "Now I'm going to try a different violin to use with the quartet just so I don't have to put my violin through this all the time."

When she isn't touring, Ibragimova lives in Greenwich, England with her husband, the Guardian music critic Tom Service. The couple married in the spring, having first met when he interviewed her. She says it isn't difficult having a critic around who is constantly evaluating music. And there are perks: "There are so many books now at home. It's great. He knows all the opus numbers."

Video: Kim Nowacki; Audio: Irene Trudel; Interview: Jeff Spurgeon; Text & Production: Brian Wise

The experience with very old instruments also forced them to rethink their approach to Beethoven's music. "All of the sudden, the relation between the cello and the piano is completely different," Haimovitz tells host Elliott Forrest. "No longer am I trying to project over the grandeur of a Steinway grand but I'm actually having to make room for the piano."

"You have a lot more leeway in terms of expressivity and color, even in the sense of one note having a shape to it," added O'Riley.

The album features Beethoven's complete works for cello and keyboard, with O'Riley playing on a fortepiano made in 1823 and Haimovitz outfitting his 1710 Goffriller cello with ox-gut strings, a rosewood tailpiece and a period bow.

The duo's performance in the WQXR studio marked a return to (mostly) modern equipment – with a 1940's Steinway and a modern cello bow – but two movements from the Opus 102 No. 2 sonata had a lightness and transparency that suggested time diligently spent in the period-instrument camp.

As Haimovitz notes, the Opus 102 sonatas "offer a window into Beethoven's late period where he's deconstructing all of the ideas of the enlightenment and what he inherited from Haydn and Mozart and really finding his own voice complete." Below is the third movement.

O'Riley and Haimovitz have previously collaborated on "Shuffle. Play. Listen" (2012), an album of pieces by classical composers (Stravinsky, Janacek, Martinu) along pop acts (Radiohead, Cocteau Twins, Arcade Fire), among others. Both artists have sought to blur the lines between pop and classical over the past decade or more – since Haimovitz began playing Bach in bars and clubs in 2002 and O'Riley started arranging arty rock songs around the same time.

Together the duo is planning a future project of pop songs given classical reworkings by contemporary composers. According to O'Riley, it will include John Corigliano's resettings of Bob Dylan and Joni Mitchell songs; Philip Glass arranging the Velvet Underground; and Gunther Schuller taking on the band Guided by Voices. A recording is expected to be out this fall.

Haimovitz and O'Riley also don't shy away from lush, romantic works as well, as their final performance in the WQXR studio demonstrates: the Andante from Rachmaninoff's Cello Sonata, Op. 19. Watch that below and listen to the full segment at the top of this page.

Video: Kim Nowacki; Sound: Irene Trudel; Text & Production: Brian Wise; Interview: Elliott Forrest

The latest group to explore this hybrid is the Jake Schepps Quintet, a string band whose members are steeped in bluegrass spontaneity but whose repertoire – yes, repertoire – is by composers from the modern classical tradition. They include Matt McBane, Marc Mellits, Gyan Riley, and Matt Flinner. Led by Schepps, a Colorado-based banjoist, the group came to WQXR to play three pieces from "Entwined," their debut album.

"Most of the instruments in the string band aren't foreign" to classical composers, said Schepps, in an interview with host Terrance McKnight. "Most classical composers have written for violin, guitar, and bass, and a mandolin is tuned like a violin so it's familiar territory."

The quintet's set began with Flatiron VII: Planetary Tuners by Mellits, a Chicago-based composer whose works have been performed by the Orpheus Chamber Orchestra and Kronos Quartet, among other groups.

Schepps has been at the forefront of melding bluegrass with other genres for several years. He previously recorded an album of Béla Bartok's music arranged for a string band, "An Evening In The Village," and says he wants to play the music of Henry Purcell for a future project. "I fell in love with his three and four-part fantasias," he said. "I love Baroque music and Bach. I'm always curious for places that I can take string band instruments into new terrain." Schepps added that it's a "lateral step" to transfer pieces from Purcell's viola da gambas to the five-string banjo.

The quintet's next selection is the album's title track, by Matt McBane, a Brooklyn violinist and composer who directs the Carlsbad Music Festival in California and whose music has been played by a number of new-music groups.

Flinner, who plays mandolin in the quintet, composed the last selection in the set, called Migrations. He tells McKnight that his challenge "was trying, as a bluegrass musician, to write across that line in a long-form manner. Classical music goes so many different directions these days. One thing that we could use more of is more American roots elements added to that. Bluegrass is a uniquely American art form. It feels like it's getting more respect."

Schepps added: "My hope is that a classical audience will come to find something interesting about bluegrass."

Listen to the full interview and performances at the top of this page.

Jake Schepps Quintet Personnel:

Jake Schepps: five-string banjoMatt Flinner: mandolinRyan Drickey: violinJordan Tice: acoustic guitarAndrew Small: double bass

Videos: Kim Nowacki; Audio: Irene Trudel; Production: Brian Wise; Interview: Terrance McKnight; Production Assistance: Rebecca Stein

The Swiss cellists Thomas and Patrick Demenga appear to take their collaboration with a more easy-going attitude. Some 35 years since graduating from Juilliard and the Bern Conservatory, respectively, they are still going strong, and performed together in December at the Chamber Music Society of Lincoln Center.

"We can go on stage and close our eyes and start without even looking at each other," Patrick Demenga told host Jeff Spurgeon. "We are so close in a way musically that we trust – it's one of the most exciting experiences that you can have on stage."

The two cellists, who also have active solo careers, came to the WQXR Café to perform as both a duo and as a trio with the Slovenian accordionist Luka Juhart. Their program combined the music of Bach with two modern works. First up was a transcription of Bach's Sonata in G minor for Gamba and Harpsichord (first movement), with Juhart playing the harpsichord part.

"Normally if you play with harpsichord and continuo," said Thomas Demenga, "you have a very thin sound and you have to be very careful as a cellist not to overpower the harpsichord. In this combination with accordion you have a really full range because he can sustain the lines so you have the full polyphony."

  Juhart met the Demenga brothers through a composer friend, which led to some festival dates in Europe. At an appearance in Austria last year, David Finckel, the artistic director of the Chamber Music Society of Lincoln Center, heard the trio and booked them on his series. Although the accordion is a relative outsider in U.S. chamber music circles, Juhart estimates that there are 30 or 40 college-level training programs in Europe where one can major in the instrument (he teaches at the academy in Ljubljana, Slovenia).

Below, Juhart performs Vinko Globokar’s theatrical solo piece, Dialog über Luft.While Juhart has sought to explore the outer boundaries of the modernist accordion sound, he has also taken up Baroque works by Rameau, Handel, Scarlatti and Frescobaldi. The Demenga brothers, meanwhile, have been equally versatile, as seen in the last work on their program, an excerpt from Thomas Demenga's Solo per due, which features all manner of bowed and plucked techniques.

"It's a bit jazzy but not really because I don't like classical musicians who try to play jazz," said Thomas Demenga. He notes that one of his classmates and friends at Juilliard was the violinist Nigel Kennedy, known for a freewheeling forays into popular styles. "We played on the streets [of New York] to make money," Demenga recalls. The two musicians also played frisbee in the halls of Juilliard. "People hated us," he said with a laugh.

Video: Kim Nowacki; Audio: Chase Culpon; Production & Text: Brian Wise

Eleven members of the choir, led by music director Fernando Malvar-Ruiz, visited the WQXR studios early this month to present a selection of carols and songs. The ensemble began with "Mary Had a Baby" and "We Wish You a Merry Christmas."

Based in Plainsboro, NJ, the American Boychoir is one of two accredited boychoir boarding schools the United States, the other being the Saint Thomas Choir School in Manhattan. The group, which marked its 75th anniversary last year, is characterized by a unique sound and facility in a wide range of styles.

Specifically, unlike the famous Vienna Boychoir, on which it was originally patterned, the American Boychoir uses so-called voices-in-transition. "That's what distinguishes us from almost any other boychoir in the world," said Malvar-Ruiz. "It's the fact that we have changing voices still singing with us. It's adding that new color that makes our sound so unique."

This allows the ensemble to fill out SATB (soprano, alto, tenor, bass) choral arrangements (and beyond), as we hear below in these performances. But as 12-year-old chorister Douglas Butler explains, the choir's sound is also the product of hard work, with a school day that stretches from 8 am to 6 pm. "We've tacked an extra three hours at the end of every day for a rehearsal," he says. "We have to learn a lot of music and a lot of times we have to do it quickly" – and by memory. Below: Bach's Domine Deus:

The American Boychoir is the centerpiece of a forthcoming film called "Boychoir." Directed by Academy Award-winning film director Francois Girard, it stars Dustin Hoffman and Kathy Bates in a feel-good tale about a troubled boy from Texas who attends the American Boychoir School. Due for national release in 2015, it garnered raves at its Sept. 6 premiere at the Toronto Film Festival.

"We did three weeks of filming and a few more weeks of recording the soundtrack," said Malvar-Ruiz. The film was shot at Connecticut’s Fairfield University and in New York, but the American Boychoir School's uniforms, logo and identity are to be used. This is just the latest Hollywood encounter for a choir whose performances have been featured in numerous films and commercials since its founding in Columbus, Ohio in 1937.

The choir has been steeped in holiday music throughout its history – at least since its first appearance in a national television broadcast of Gian Carlo Menotti’s opera, Amahl and the Night Visitors, in 1951. Among its performances this month is an appearance at the Metropolitan Museum of Art on Dec. 16. Watch their fourth WQXR performance below and listen to the full segment, with host Terrance McKnight's interview, at the top of this page.

Video: Kim Nowacki; Audio: Irene Trudel; Production & Text: Brian Wise

Stravinsky himself was said to compose not at a concert grand, but "at a tacky-sounding and usually out-of-tune upright piano that has been muted and dampened with felt,” according to a onetime description by his wife, Vera Stravinsky. What’s more, Stravinsky’s teacher, Rimsky-Korsakov, advocated using uprights in orchestra works, arguing for their tinny, delicate sounds over thick, chordal opulence. The instrument may have also underscored the Russian folk sounds that characterize many of Stravinsky's early works.

Weilerstein, who is a 2011 recipient of the MacArthur "Genius" grant and a busy touring artist, performed what she described as "one of the most beloved pieces for cello," the Gigue from Bach's Cello Suite No. 3:

Thoughts about the weather were further put aside when Weilerstein brought up her latest recording, an all-Dvorak affair that includes the Cello Concerto along with several miniatures (read more and get a free download here). She recorded the concerto last summer in Prague with the Czech Philharmonic. "There’s a kind of warmth and depth to their playing which I found very unique,” she said of the orchestra's sound.

When a long-established string quartet brings in a fifth collaborator, questions inevitably arise: how will the four players interact with the newcomer? Who will call the shots in rehearsals, and how does the group dynamic change?

When Béla Fleck came to the WQXR Café, curious staff members began asking about his repertoire. Would he be playing Scarlatti or Scruggs? A Bach invention or a bluegrass breakdown?

Imani Winds was a novelty when it first arrived on the scene in 1997, a wind quintet that veered away from the customary European classical fare to focus on compositions drawing from African and Latin American styles and idioms. Composers like Astor Piazzolla, Paquito D’Rivera and Wayne Shorter were the group's mainstays. So were arrangements of spirituals or songs by jazz singer Josephine Baker.

Richard Stoltzman really wants to feel that he's connecting with his audiences – even if it means resorting to nudity.

Seated in the WQXR Café with his baritone guitar in hand, Verdery lets introspective pieces by Bach and Randy Newman spill forth with a hushed introspection.

The iconic, boxy taxis, of course, have long been absent from New York City streets but the musicians could be forgiven for the oversight. The London-based quartet was in town for their first New York appearance since 1995. The longtime absence is something of a puzzle, as group has maintained an active presence in the UK. The quartet has released major recording projects that have received awards from the British press, appeared on BBC radio and television, performed at the Proms in London and toured through Europe and beyond.

Jan Vogler is often identified as a German cellist but in many ways, he’s a quintessential New Yorker: he lives on the Upper West Side with his wife and two daughters, enjoys jogging in Central Park and biking along the West Side Highway, and speaks impeccable English in an enthusiastic, rapid patter. He married his wife, the violinist Mira Wang, downtown at City Hall.

Somewhere along the way in her 20-some year career, Jennifer Koh jumped off the violin soloist treadmill in favor of less familiar paths and creative channels.

If Franz Liszt were alive today, he may find a certain kinship with Chilly Gonzales. The German-based Canadian pianist and composer is the current holder of the world record for longest solo concert, at 27 hours, 3 minutes and 44 seconds. He has crowd-surfed at a BBC Symphony concert in London, challenged the rocker Andrew W.K. to a piano battle (and won), and has pioneered his own brand of “orchestral rap.”

Maya Beiser has been pushing her cello to the edge of avant-garde risk-taking since the early 1990s. Composers as diverse as Steve Reich, Osvaldo Golijov and Tan Dun have written works especially for her, and she was a founding member of the Bang On A Can All-Stars. Her Twitter account is called "Cello Goddess" and one of her crossover successes is an arrangement of the Led Zeppelin tune "Kashmir."

Making recordings of quiet, spiritual music from the 16th century isn't so easy in 21st-century New York. So to record its last album, "Endbeginning," the all-male vocal ensemble New York Polyphony traveled to a medieval church in rural Lanna, Sweden. There the noise floor – the technical term for background noise – was exactly zero. In New York City, it's around 40 decibels.

When you think mandolin, bluegrass pickers and old-timey music frequently comes to mind – Bill Monroe, Sam Bush, Jerry Douglas or Chris Thile. But when Avi Avital sat down to play in the WQXR Café, the sounds of a Bach cello suite filled the air. Then came the strong mournful strains of Ernest Bloch's Nigun, a variation on an ancient Hebrew melody written for the violin.

Steven Isserlis, the English cellist and a guest in the WQXR Café, said that he’d like to write a book about what it’s like to be a professional musician. He's not the first with that idea but one expects he’d have a lot to say.

Ryu Goto opened his Café Concert with Fritz Kreisler's Liebesleid (Love's Sorrow), a bittersweet waltz that evokes a kind of aristocratic grace from another era. But Goto is hardly a violinist stuck in the past.

Franz Schubert's short, hectic life was full of "what ifs" -- unfinished sketches, abandoned works and fragmentary thoughts. Many of these leftovers were quite extraordinary despite their obvious limitations.

Some very successful musical collaborations have been built on shaky personal relationships. Gilbert and Sullivan disliked each other and rarely met. Renata Scotto often sang beautifully with Luciano Pavarotti, but excoriated him in her autobiography.

The team of violinist Joshua Bell and pianist Jeremy Denk appears to be different. “Finding the right musical partner is like making best friends,” Bell said. “You make them throughout your life, you sometimes fall into them, but in the end you don’t have a lot of really, really great friends. You have a handful and Jeremy is one of mine.”

Denk concurs. “It’s like when you are talking with someone and you feel this kind-of instant sympathy or empathy.”

Classical musicians often are known to gush around interviewers but Denk and Bell have a track record to back up their mutual admiration society. Both attended Indiana University, but just as Denk entered the school in 1990, Bell had already graduated. The latter was on his way to a big career as a soloist and violin pin-up god.  

But like two ships passing in the night, Bell and Denk kept tabs on each others’ careers. When they finally performed together – playing the Grieg Violin Sonata at the 2004 Spoleto Festival in Charleston, S.C. – sparks flew. They've been touring regularly ever since. This month they release "French Impressions," their first recording, which consists of violin sonatas by Saint-Saens, Franck and Ravel.

In the WQXR Café, Bell and Denk played the blistering finale from Franck’s Sonata in A Major. Bell surmised that he's performed the work "at least 1,000 times," which isn’t entirely surprising. Franck wrote the piece as a wedding present for Eugène Ysaÿe, who gave its premiere. Ysaÿe then taught Josef Gingold, who in turn taught Bell at Indiana (where Bell now holds a professorship himself).

The new recording also marks a turning point: Bell’s last release for Sony, “At Home with Friends,” was a smorgasbord of classical, pop, Latin jazz and film-music arrangements (Denk appeared on one track); Denk’s recent recordings have focused on knotty works by Schoenberg and Stravinsky.

The two artists decided to record "French Impressions" not in a traditional studio but at the Musical Instrument Museum in Phoenix, AZ. “Recording is scary because you know it’s going to be down forever,” said Denk. “Especially for this music – it’s so much is about the sound and the color and the pallet of colors from both instruments. That’s very important for us to make sure we have the right sound.”

Tune in to WQXR to hear more performances of Joshua Bell & Jeremy Denk on Jan. 10 at 8 pm.

Video: Amy Pearl; Sound: Edward Haber; Interview: Elliott Forrest; Text: Brian Wise

While chatting with Charlie Siem, one gets the feeling the English violinist is yearning to quote that old shampoo commercial: Don’t hate me because I’m beautiful.

On a recent spring afternoon in the WQXR Café, Arabella Steinbacher tore through Ysaye's Obsession. Then she turned her attention to Kreisler’s Recitative and Scherzo. While the works are not known for their calm sensibilities, Steinbacher capped off her virtuoso performance with an accidental whack of an overhanging lamp. Her bow was left with several horse hairs drooping. "It’s really annoying when that happens in the middle of a concert,” Steinbacher said, laughing. “It interferes with the performance.”