The musical icons first collaborated last year to perform “Rhapsody in Blue” during the 50th annual Grammy Awards, at which Mr. Hancock won the night’s top honors for his Joni Mitchell tribute album, “River: The Joni Letters.” The two joined forces again this year for an international summer concert series that spanned Europe, Canada and the United States and concluded this month at the Hollywood Bowl in Los Angeles. In a Time magazine essay introducing Mr. Lang to the magazine's 2009 list of the world’s 100 most influential people, Mr. Hancock described his touring partner’s musical style as sensitive and deeply human. “You hear him play, and he never ceases to touch your heart,” Mr. Hancock said of Mr. Lang. “And he’s fearless. He’s not afraid to burst the bubble of false elitism. He’ll wear a new kind of tux, with tennis shoes. That’s cool.”

ICAP was founded by Daisaku Ikeda in 2002 to support the United Nations’ International Decade for a Culture of Peace and Nonviolence for the Children of the World (2001–2010). The committee—composed of professional artists from a wide array of disciplines, many of whom are internationally known—supports humanistic nonviolence education for youth through dialogue and the unique power of the arts. Through the efforts of multi-genre guitar virtuoso and ICAP board member Carlos Santana, the committee has collaborated since 2004 with the festival to present workshops, panel discussions and dialogues related to peace and the arts, including the exhibitions “Artists as Mentors,” “Artists as Peacemakers” and “Building a Culture of Peace For the Children of the World.”

During the presentation at Stravinski Auditorium, Mr. Hancock read the award certificate, which acknowledged Mr. Lang for working “to dispel misery and injustice through the power of art and music, while building bonds of friendship and trust among people throughout the world.” The certificate gave special mention to the Lang Lang International Music Foundation, whose mission is to enrich children’s cultural lives through music. Mr. Lang received a standing ovation from the more than 4,000 in attendance.

In a surprise twist, American music legend Quincy Jones, another past recipient of ICAP’s Humanity in the Arts Peace Award, appeared onstage to offer spontaneous remarks celebrating the two virtuosos. Mr. Lang conveyed his deep appreciation for the medal, which bore the words of ICAP founder Daisaku Ikeda: “The power of art can break the shackles that bind and divide human beings."

Mr. Hancock and Mr. Lang then faced each other from their respective grand pianos, captivating the audience with a program blending classical and jazz music, and featuring selections from Ravel, Gershwin and Vaughan Williams, among others. For their final number, drawing upon Mr. Lang’s earliest musical inspiration—“Tom and Jerry”—they performed Franz Liszt’s Hungarian Rhapsody No. 2, which Mr. Lang first heard watching the cartoon in China at age 2. ICAP this year also debuted its new exhibition, “Voices of Change—Artists Speak Out” at Stravinski Hall, one of the most visible venues at the prestigious event held on the shores of Lake Geneva. The exhibition celebrates artists who choose to create and perform music that makes an impact on society. Mr. Nobs, the festival founder, expressed his gratitude to Mr. Ikeda and ICAP for their continued contributions to the annual event, which celebrated its 43rd year.