Jamie Foxx wanted to entertain a group of musically inclined high school students with a few bars from his Grammy winning hit, “Blame It.” But since the song is an ode to the effects of alcohol, he changed the lyrics to “Blame it on the a-a-a-apple juice.” The kids roared. “I changed it so you guys could sing it,” he joked. Students from four high schools gathered Tuesday at Walt Disney Concert Hall, where Foxx helped present new violins, flutes, French horns, trumpets and drums valued at $500,000 to students from 16 schools nationwide. The instruments are part of the Fidelity FutureStage program, an effort by the investment firm to enrich arts education in public schools. Founded in 2006, the program provides instruments, specialized training by professional musicians, and a chance for aspiring artists to perform with renowned orchestras such as the Los Angeles Philharmonic and Boston Pops. Foxx told students he began as a classical pianist and eventually won a scholarship to study the instrument in college. Foxx, 42, who won an Oscar for his portrayal of Charles in “Ray,” got the crowd fired up and had them chanting “mu-sic, mu-sic” before students came on stage to accept shiny new saxophones, clarinets and other instruments.