Classical Janacek, Leos: Sinfonietta; Taras Bulba. Vienna Philharmonic Orchestra, Charles Mackerras, conductor. (London Digital LDR-71021). Philharmonia Orchestra , Simon Rattle, conductor. (Angel Digital DS-37999) - Janacek's two mighty orchestral works - ''Sinfonietta,'' a tone poem of reminiscenses of his youth in Brno, and ''Taras Bulba,'' his testament to fighting for freedom - are often paired on discs. Both pieces are stiff challenges for recording engineers and, if properly put to record, challenging for the home stereo as well! Mackerras, who has been recording the major Janacek operas with the Vienna Philharmonic, offers his authoritative views on these two works as well. They are kissed with authenticity: Mackerras studied in Prague and heard all the music performed there and in Brno. The ''Prague Style,'' Mackerras once noted, put smoothness as the ideal, while the ''Brno Style'' favored the rugged, even rough quality inherent in the music. Mackerras is clearly a ''Brno Style'' man; he rightly saw that school to be truer to the composer's compositional style and coloristic intentions. The Vienna Philharmonic does not play beautifully in a classic sense , for this music is meant to be brusque, craggy, rough edged. They do what Mackerras asks in a most important way, and the London engineers get it all cleanly into the grooves.
Simon Rattle, on the other hand, favors the ''Prague Style,'' taking an emery board to all the roughness - almost as if he were trying to make a case for the composer as a Czech Elgar. The result is a bit craggy, somewhat majestic, but generally too smooth, too tame. Curiously, the Philharmonia does not play as well as it might - particularly in the ''Sinfonietta,'' where the brass outpourings are less precise than they should be.