Question: Gaston Dufresne had an American composer student who was described as what?

Context paragraphs:
Gaston Dufresne: Gaston Dufresne (September 9, 1898 – December 6, 1998) was the principal bassist in the Boston Symphony Orchestra from 1927 to 1957 and with the Florida West Coast Symphony from 1963 to 1979.  He also taught solfège, a singing technique used to teach pitch.  Among his contrabass students were American composer Leroy Anderson and Boston Symphony principal trumpeter Roger Voisin.  Dufresne taught solfège to Voisin and to Boston Symphony hornist Richard Mackey.

Carl McKinley: Carl K. McKinley (9 October 1895 in Yarmouth, Maine – 24 July 1966 in Centerville, Massachusetts) was an American composer of classical music.  Born in Maine, he spent some time in Paris on a Guggenheim Fellowship.  He studied music at Harvard University, and was granted a Naumberg Fellowship to study in New York City for the 1917-1918 school year.  There he worked with Rubin Goldmark, Gaston Dethier, and Walter Henry Rothwell.  He later played the organ in a church in Hartford, Connecticut, after which he spent four years playing the instrument in New York's Capitol Theatre.  In 1929 he became a member of the faculty of the New England Conservatory of Music.

Transformations (opera): Transformations is a chamber opera in two acts by the American composer Conrad Susa with a libretto of ten poems by Anne Sexton from her 1971 book "Transformations", a collection of confessional poetry based on stories by the Brothers Grimm.  Commissioned by Minnesota Opera, the work, which is described by its composer as "An Entertainment in 2 Acts", had its world premiere on 5 May 1973 at the Cedar Village Theater in Minneapolis, Minnesota.  Anne Sexton, who had worked closely with Susa on the libretto, was in the audience.  It went on to become one of the most frequently performed operas by an American composer with its chamber opera format of eight singers and an instrumental ensemble of eight musicians making it particularly popular with smaller opera companies and conservatories.  The 2006 revival production of "Transformations" at the Wexford Opera Festival won the "Irish Times" Theatre Award for Best Opera Production.

George Strong (composer): George Templeton Strong (May 26, 1856 – June 27, 1948) was an American composer of classical music and a professional painter.  His work has been described as Romantic.  He moved to Vevey, Switzerland, in 1897 and lived there and in Geneva for the remainder of his life.  Although his career was in Europe, he is considered an American composer.

Leroy Anderson: Leroy Anderson ( ~ ); (June 29, 1908 – May 18, 1975) was an American composer of short, light concert pieces, many of which were introduced by the Boston Pops Orchestra under the direction of Arthur Fiedler.  John Williams described him as "one of the great American masters of light orchestral music."

Hoagy Carmichael: Hoagland Howard "Hoagy" Carmichael (November 22, 1899 – December 27, 1981) was an American composer, pianist, singer, actor, and bandleader.  American composer and author, Alec Wilder, described Carmichael as the "most talented, inventive, sophisticated and jazz-oriented of all the great craftsmen" of pop songs in the first half of the twentieth century.  Carmichael is one of the most successful of the Tin Pan Alley songwriters of the 1930s, and was among the first singer-songwriters in the age of mass media to utilize new communication technologies, such as television and the use of electronic microphones and sound recordings.

Gaston Glass: Gaston Glass (December 31, 1899 – November 11, 1965) was a French-born American actor and producer.  He was born Jacques Gaston Oscar Glass in Paris and died in Santa Monica, California.  He was the father of the composer Paul Glass (born in 1934).

Gaston Serpette: Henri Charles Antoine Gaston Serpette (4 November 1846 – 3 November 1904) was a French composer, best known for his operettas.  After winning the prestigious Prix de Rome as a student at the Paris Conservatoire, he was expected to pursue a career in serious music.  Instead, he turned to operetta, writing more than twenty full-length pieces between 1874 and 1900.  He accepted some conducting work and also served as a critic and journalist on a number of French newspapers and magazines.

Jean Dufresne: Jean Dufresne (14 February 1829 – 13 April 1893) was a German chess player and chess composer.  He was a student of Adolf Anderssen, to whom he lost the "Evergreen game" in 1852.

Vanessa Lann: Vanessa Lann is an American composer living in the Netherlands.  She is known for contemporary compositions for underutilized instruments such as the clarinet, bassoon and toy piano.  Her compositions have been broadcast on radio, recorded on compact discs, and performed in music festivals in Europe and North America.  She has written numerous types of compositions, including concertos and operas.  In 1990, she was musical director at the American Repertory Theater.  Reviewer David Toub described her music as "expertly performed". " New York Times" music reviewer Allan Kozinn described her composition "Is a Bell ... a Bell?"  as a "propulsively rhythmic score" which was charming with its use of two toy pianos to bring out "different timbral qualities."  Music reviewer Jed Distler described her compositions as "gracious keyboard writing and humor."  Dutch music critic for the prominent daily newspaper "de Volkskrant", Frits van der Waa, has reviewed her music on numerous occasions.  He described her half-hour opera "The Silence of Saar" in 2013 as an "endless series of mind-numbing variations," he described her music in 2005 as "intense but sweet juicy tension," and her composition for the Delft Chamber Music Festival in 2007 as "beautiful."

Supporting paragraphs: Gaston Dufresne Leroy Anderson
Answer: one of the great American masters of light orchestral music