“Whimsical and romantic, the music of Icelandic singer and cellist Laufey Lín Bing Jónsdóttir, or Laufey, blends pop, jazz, classical and bossa nova – a “mishmash,” she calls it, which has led to sold-out exhibits, bestselling albums, and a Grammy Award. Along with her third album, “A Matter of Time,” being launched this week, she sits down with correspondent Tracy Smith to debate her musical tastes; her response to the response of younger followers; and the joys of singing a duet with Barbra Streisand of a music she composed, “Letter To My 13-Yr-Outdated Self.” from the video introduction