Feb. 11, 80.AT a good concert to-night in the foyer of the opera house, Philadelphiathe band a small but first-rate one. Never did music more sink into and soothe and fill menever so prove its soul-rousing power, its impossibility of statement. Especially in the rendering of one of Beethovens master septettes by the well-chosen and perfectly-combined instruments (violins, viola, clarionet, horn, cello and contrabass,) was I carried away, seeing, absorbing many wonders. Dainty abandon, sometimes as if Nature laughing on a hillside in the sunshine; serious and firm monotonies, as of winds; a horn sounding through the tangle of the forest, and the dying echoes; soothing floating of waves, but presently rising in surges, angrily lashing, muttering, heavy; piercing peals of laughter, for interstices; now and then weird, as Nature herself is in certain moodsbut mainly spontaneous, easy, carelessoften the sentiment of the postures of naked children playing or sleeping. It did me good even to watch the violinists drawing their bows so masterlyevery motion a study. I allowd myself, as I sometimes do, to wander out of myself. The conceit came to me of a copious grove of singing birds, and in their midst a simple harmonic duo, two human souls, steadily asserting their own pensiveness, joyousness.