Foremost among conductor Christoph Eschenbach’s pet causes is the art of the lied, a 19th-century German form that fuses poetry and music. Next week at Ravinia, he’s scheduled two lieder recitals, one featuring a veteran (Tuesday) and one featuring a young Turk (Thursday); he’ll accompany both on the piano. My bet is on the former, German tenor Schreier, who is one of the most accomplished singers around–though Danish baritone Bo Skovhus is no slouch either. Both men will be singing the works of Schubert and Schumann, but what sets Schreier apart is his interpretive acumen–which is razor-sharp after decades of thinking and rethinking the core repertoire. This will be particularly important when it comes to Schubert’s various songs set to Goethe’s poems. The young, unassuming Schubert’s admiration for the writer was unrequited. Though he repeatedly set and dedicated songs to Goethe–most of which, like the Gesange des Harfners, are musically sophisticated and psychologically revealing–he never got a response. Schumann’s Eichendorff Liederkreis–a dozen numbers set to text by Joseph, Baron von Eichendorff–displays the composer’s knack for mimicking the sounds of nature and shifting points of view. Schreier–who’s doing triple duty as a voice coach at Ravinia’s Steans Institute for apprentice musicians and as a soloist in a Chicago Symphony concert–has the skills to delineate its myriad moods and levels of meaning. Tuesday, 8 PM, Martin Theatre, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park; 728-4642