Wandelweiser is a group of modern classical composers and performers finding great influence in John Cage. Silence and restraint are equally important as sustained tones in the ambient works. Swiss clarinetist Jürg Frey is a key figure in the minimalist movement, and he will pop in for this celebration of Wandelweiser. On Saturday, local new-music group a.pe.ri.od.ic will play from its debut CD, a collection of Frey works, with the man himself. On Sunday, pianist R. Andrew Lee shows his gentle hands. This event is presented by a.pe.ri.od.ic and the Frequency Series, and it's the rare event where we can say that we hope it rains. It just fits the moon of these melancholy works.