The other big discovery was guest conductor Sarah Ioannides, a Curtis Institute graduate and someone who has been working with regional orchestras from El Paso to Tacoma. However gracious her manner, she somehow induced Chamber Orchestra of Philadelphia to play on a level that’s been wanting since the departure of now-conductor-laureate Ignat Solzhenitsyn some years ago. The playing in this longish Beethoven program was vigorous, solid, and with an unusually vibrant sonority. Her programming ideas were provocative: She programmed a lot of early Beethoven that’s worth an occasional hearing, such as the Rondo for piano and orchestra, as well as unfinished Beethoven, in an assemblage of his borderline-chaotic Symphony No. 10. Her rendering of that last piece was particularly notable: This is music with no real performance tradition, though you wouldn’t have known that from what was heard on Sunday.