Born in Puerto Rico in 1953, Roberto Sierra continued his education in England and Germany, and then worked with György Ligeti in Hamburg for three years. Sierra calls his fusion of European modernism and Latin American folk elements "tropicalization."

Alegría, commissioned and premiered by the Houston Symphony Orchestra in 1996, is a perfect example of this. Fleet, tonally centered, and brightly colored, it expresses alegría (happiness) with joyous orchestral exuberance. Its rapid pulse plays rhythmic games with the fact that six beats can be stressed as either two groups of three or three groups of two, a characteristic of much Hispanic and Latin American music. Occasionally the euphoric whirl takes some of the musicians beyond the measured bounds, as Sierra asks players to rush a pattern as fast as possible, independent of the rest of the orchestra. Sierra contrasts different sections of the orchestra and different dynamic levels, and pushes the excitement envelope with uneven accents and a pell-mell 5/8 dash to the final cadence.

- John Henken is the Philharmonic's Director of Publications.