Public radio stations and NPR are promoting April as Public Radio Music Month, a campaign designed to raise awareness of the cultural contributions of pubradio’s music stations and the role federal funding plays in keeping those outlets on the air. Stations that broadcast classical, jazz and contemporary music formats have scheduled special concerts throughout the month to highlight the diversity of programming and the field’s commitment to presenting new artists. Musicians themselves are participating — and not just by performing at station events. Nearly 130 artists — including the Black Keys, the Decemberists, My Morning Jacket and the Roots — signed a “love note” to public radio, expressing thanks to local stations that play their music. NPR calculates that more than 180 public radio stations are devoted to noncommercial music formats such as classical, jazz, blues and bluegrass, and another 480 include music in their programming lineups.