To mind, it is the competitive formalism of SPEBSQSA that limits and deadens the genre. In certain ways, it's laudable: "preservation" is in the name, after all, and judging can be more objective when the criteria are well-known by all in advance. Amateurs are drawn to the cozy and familiar, a definable target to aspire to.

But when quartets are allowed to do the equivalent of free-styling, that's when they most sparkle and amaze, and the repertoire diversifies. Several times I've been tempted to try barbershop, electrified by a few groups at a showcase, but the thought of having to perform the core repertoire in the standard style stops me dead.

Of course, there's doo-wop, but doo-wop groups also suffer from a narrow style and choice of material. It seems you have to join a large chorus in order to sing a real diversity of music in a group, and then you have all the restrictions and artificiality of that environment, with little choice about the material.

Why do we have no a cappella small-group tradition that caters to a real diversity of music: madrigals, glees, art songs, minstrel songs, folk songs, barbershop, ragtime/novelty, swing, doo-wop, jazz, pop...? I can only think of two small groups that have made forays into a fair variety of genres: The Manhattan Transfer and The King's Singers.