Alma describes a 1904 concert in Amsterdam in which Mahler 's Fourth Symphony was performed twice .
Alma claims that Mahler , after conducting the work in the first half , handed the baton to Mengelberg for the evening 's second performance .
Describing a 1904 concert in Amsterdam in which Mahler 's Fourth Symphony was performed twice , Alma claims that Mahler , after conducting the work in the first half , handed the baton to Mengelberg for the evening 's second performance .