Time was when an evening string-quartet music usually foretold an experience in exquisite intellectually: music subtle and well-crafted, if a tad desiccated now and then, soft-toned and oh-so-proper; received in awed silence by an audience elderly and respectful of the Great Masters they had come to venerate. Then came the Kronos Quartet, whose work over its 13 years of spellbinding, iconoclastic music-making has blown the whole concept of chamber music off the shelves and onto the charts.

Consider the latest Kronos release, Pieces of Africa, the group’s 10th. Where on any other string-quartet performance would you find the basic ensemble of two violins, viola, and cello complemented by an exotic array of African instruments, including delicate percussion and extravagantly designed strings with names like sintir, ngoma, donno, hosho, and oud? Or complemented by a gospel choir? Or with solo singers, including members of the quartet itself, unpolished in tone but eager and, presumably, proud? It’s all here, and the results are, mostly, sheer enchantment.

Founded in 1973 by violinist David Harrington, unchanged in membership — second violinist John Sherba, violinist John Sherba, violinist Hank Dutt, and cellist Joan Jeanrenaud — since 1978, the Kronos has a healthy disregard for chamber music’s more effete values. Some doubters take the Kronos’ concentration on 20th-century scores as an attempt to shirk classical composers like Beethoven. But the sheen of the group’s music-making, the intensity of its approach to such latter-day classics as the steaming, haunted late quartets of Dmitri Shostakovich, still these arguments. The main difference between the Kronos and the rest of the chamber-music world, in fact, seems to be that — defying all traditions of string-quartet behavior — the Kronos folks always seem to be having fun.

Pieces of Africa, released on a CD decorated with a colorful African pattern, zestfully proclaims that. The continent’s current contributions to the pop world are well known, from the exuberant uproar of South Africa’s Ladysmith Black Mambazo to the complex, pounding rhythms of Senegal’s Youssou N’Dour. The alliance of the Kronos and composers from seven regions of Africa suggests a joyful entry into classical music as well.

Most of the works on the album are quite short: They’re tone pictures often directly related to their composers’ lives. Zimbabwe’s Dumisami Maraire fashioned his quiet, songlike ”Mai Nozipo” as a portrait of his mother. In his four-minute ”Sunset,” Gambian composer Foday Musa Suso adds the skittering sounds of his 21-string kora to the needle-shower pizzicato of the quartet, creating a miniature tone poem that, as Suso says, depicts the festive rush of social activity in a village at twilight when ”people like to get into the groove.” In a harrowingly beautiful 12-minute piece called ”Water Wheel,” Sudansese-born drummer Hamza El Din creates a lament for his native village, which was flooded, and its people forced to relocate, after the Aswan High Dam was built. Waves of solemn, simple melody seem to pour over a musical reflection of a slow-turning, primitive mill wheel, its throb accentuated by the steady beat of El Din’s tar (a small hand-held drum).

Ironically, it’s the piece closest to Western concert styles, Kevin Volans’ ”White Man Sleeps,” that with its self-conscious dabs at minimalism is by some distance the least appealing part of the collection. But otherwise the record is pure Kronos: delightful, imaginative, out-of-the-way music played with the same loving care the group might lavish on a Beethoven quartet, if they ever decided to play one. The works may be small; the results are anything but. A