Misc: In Physics, what type of length is represented by the small Greek letter "lambda"?

Questions

Who was Louis Moreau Gottschalk?

In what city was Tchaikovsky's Piano Concerto No. 1 in B-flat minorgiven its world premiere?

Who wrote the 1829 opera William Tell?

A feature of Franz Schubert's life was the Schubertiad. What was it?

For what two solo instruments did Brahms write his DoubleConcerto in A minor Op. 102?