Poof. Though the line drawings are engaging, this is the merest trifle about the miniature dachshund of cellist and conductor Mstislav Rostropovich--who goes everywhere the Maestro goes, ""has her very own passport,"" and, yearning for an instrument to play too. . . one night jumps up on the piano bench and pounds away. Whether we're supposed to thinks Pocks is actually trying to perform is unknowable from the half-literal, half-whimsical text and the otherwise not unlifelike cartoons. In any case, it's no more than a wisp of an anecdote--and, for hilarious, authentic concertizing, not a patch on The Philharmonic Gets Dressed, by Karla Kuskin and Marc Simont.