The name Kroll has a distinctive ring in clarinet circles as Oskar Kroll&rsquo,s book on the clarinet has been regarded as one of the standard treatises on clarinet playing ever since its first edition in 1944.Karl Kroll (1881-1957) - father of the author Oskar and teacher of the editor Dieter Klöcker - enjoyed a considerable reputation as a clarinettist during his lifetime.The '20 Caprices' are short pieces, musically indebted to the late Romantic period, but incorporating a number of tricky fingerings.