In Saturday night’s double bill with Berta Rojas, John Williams approached the musical terrain of the Venezuelan maestro Agustín Barrios Mangoré with the caution of an explorer in exotic regions—a caution not far removed from the daring of the adventurous tourist. On Sunday night, sharing the stage with Paco Peña, Williams approached the more familiar territory of southern Spain with the enthusiasm of the regular visitor who speaks the language and knows the people, and for whom familiarity breeds respect.

Williams and Peña have been friends and collaborators since the late Sixties. They have cross-fertilized each other’s styles, with Peña adding a Williams-like tonal refinement to the attacking Flamenco style, and Williams adding a little of the Peña edge to his diplomatic manner. Williams was more at ease tonight, walking onto the Wanamaker’s stage and jumping straight into the loose Andalusian cadence of a composition whose English title, “Daybreak,” suggested the opening of an evening of possibilities. Being Williams, the statesman of classical guitar, he then made some friendly remarks, explained the provenance of the next two pieces, took us back to the birth of the instrument, and assembled the materials which Peña was shortly to detonate. 

“Fantasia,” by the vihuela player Luis de Milán (ca. 1500–61) and adapted for guitar by Williams, laid out the architectural framework with strong octaves and stately chording. “Canarios,” written for the comparatively new five-string guitar by Gaspar Sanz (1640–1710), was a Canary Islands dance in 5/4 time, with an emphasis on the second of the first three beats, and plenty of attack.

Another Luis de Milán composition, “Toda mi vida os amé,” formed the basis for Williams’s “Homage to Raphael.” Williams played his opening minor theme cinematically—after all, guitarists admire Williams for his technique and his elevation of the guitar to the dignity of the concert hall, but most people know him for the theme to The Deer Hunter. The second movement was bravura stuff, with skittering high triplets, Flamenco-ish descending phrases, and plenty of forceful chording in the engine room. The third movement reharmonized the first in a major key, with some smoothly executed harmonics evoking the original minor.

Having sketched the vocabulary, Williams finished with three Albéniz favorites. The tremolo and mid-voiced melody on “Asturias” were technically superb, but not all of the C chords were slashed with the requisite swagger. “Majorca,” with its tinges of Arab and Catalan influences, soaring central section, and clever re-voicings, was the highlight of the set. The finale, “Cordoba,” was marred when Williams, perhaps focusing too much on harmolodic decoration in its closing stages, didn’t get back down the neck in time and skidded across a chord.

Peña opened with a flaming response to Williams’s set, moving murkily between A-flat and D-flat before slaloming down the Andalusian cadence with profligate and fertile ease.

Paco Peña came on white-haired and white-shirted, his capo fixed at the first fret to raise the string tension, and a small black square of duct tape on the back of his guitar like a pirate’s flag. This small black square says it all. It’s an old guitarist’s trick. If you wear chunky belt buckles, or play with the guitar pressed to your body, a square of duct tape will prevent you accidentally scratching the back of the axe. They don’t teach you that in music school.

Peña established the world’s first university course in Flamenco, at Rotterdam University. Perhaps it’s possible to teach duende to the Dutch, but I doubt it. Anyway, Peña came up the old way; the right way. He grew up in the music, and learned on the stand. The first rule is, you have to own the stage. So he opened with a flaming response to Williams’s set, moving murkily between A-flat and D-flat before slaloming down the Andalusian cadence with profligate and fertile ease. The bottom string alone threw down the gauntlet: twanging vibrato, one-finger slides, and hammered-on triplets alternated with tactile and spiky flurries up top, and chords like a fall of boulders. He even worked in the lick from “Asturias.” Williams had worked through guitar selections. Peña was playing music, and letting the music play him. 

Flamenco is called folk music, but it is technically more exacting than classical guitar, and its rhythms and improvisation place it closer to jazz. Like all improvisers, Peña is a gambler. Accidents, good and bad, are the truth of improvisation. Peña’s tone on the high strings is always on the edge of failure. His nails play across the strings, delaying the notes with a scrape of tension and resistance. When it works, the notes buzz like wasps or mosquitos, or sear through the air like an arrow or an unsheathed blade.

Win some, lose some. It didn’t matter too much that at one point in this opener, Peña’s left hand shot off so fast that his right couldn’t keep up. The notes came out from the fingerboard only, hammered-on with his left fingers, while his right fingers generated only scratches. There is a peculiar, priceless candor to reaching the edge of a player’s capacity and the instrument’s compliance. Musically, it’s like the brush with death that reminds you that life hangs by a thread as narrow as a nylon guitar string.

Peña followed with a song by Ramón Montoya (1879–1949), who brought the Flamenco guitarist out from behind the singer as a solo instrument. He reinforced the jazzy associations of the sequence, F minor–A-flat minor–G minor–C—think “Love Me Or Leave Me” or “Moanin’”—by swinging the root notes on the bottom two strings, and tapping out a beat on the golpe with two fingers of his right hand. This was the rhythm; the Taranta that followed was the blues. Staying on the third and fourth strings so that the melodies touched the rhythmic roots on the lower strings, Peña digressed away from the modal line through serendipitous hints and intelligent designs, pushing for wrong notes and temporal tics, then smashing everything back together with furious six-string rasgueado strumming.

After each number, Peña stood up, frowned, looked at the floor, and proffered his guitar to the audience in humble perplexity, as if he too wondered where it all came from. He knew what he was up to. About midway, he explained the difference between “free” Flamenco styles—the guitarist makes the changes when it feels right, like the old bluesmen who played the eleven- or thirteen-bar blues—and cantes, the “songs” with fixed chord sequences. His set developed from free palos to formal ones, ending with a galloping Fandango and a relentless Soleá. The effect was to compress ever greater fluency into ever tighter form. And that made every melodic flourish and harmonic deviation more explosive.

John Williams, applauding Peña as he came on stage, joined in on the second encore. “Before you say anything, I’m an interloper,” Williams said. Peña laughed, said he didn’t know what an interloper was, and denied that Williams was out of his depth: “If I know John . . . ”

Williams, knowing that Peña could go off-road at any moment, didn’t take his eye off Peña’s fingers throughout. He kept up, too. But when Williams carried a melody in thirds on the high strings with his usual gentlemanly tone, Peña’s low harmony was so twangy and syncopated that it almost unseated him. You could see how much they were enjoying themselves.