The penultimate concert of the 2011 season at Tannery Pond was not only the occasion of one of Artistic Director Christian Steiner’s appearances as pianist, but the visit of an impressive and rather fascinating group of musicians from Southern California, the Arabella Ensemble, consisting of Lorenz Gamma, violin, Jennifer Langham, cello, Ming Tsu, piano. Mr. Steiner has enjoyed a long friendship with Ms. Langham, and they have played together often over the years. Lorenz Gamma and Ming Tsu are husband and wife. The three musicians of the Arabella Ensemble have markedly different personalities. Ms. Tsu takes a rather understated approach in her music-making, but the clarity and definition of her understanding of the music she is playing command one’s interest from the start, and there is no danger of her receding into the background. The playing of her husband, Lorenz Gamma, reflects a carefully considered, analytical musicianship. His phrasing was consistently elegant and clearly articulated. Jennifer Langham, the most outgoing of the players, played with warmth and energy, often with pungent attacks, which never distracted from the flow of her line. She appeared to function as the leader of the group, not so much through active dominance as as its heart. Often she seemed to share the lead with Mr. Gamma through exchanged glances.