Pop-Rock Gordon Lightfoot: ''Salute.'' (Warner Bros. 1-23901) - Bursting up through an album of otherwise modest, but charming folk-pop songs is ''Whispers of the North.'' Gently introduced by the sounds of birds - the predominent one sounds like the eerie call of a loon - this is a song that would hush an audience and bring a quietness, so wonderfully are Mr. Lightfoot's words of escaping to the wilderness mirrored in his music. ''Whispers of my heart / In the tracks of animals / I will leave my footprints there / To lie beneath the snow . . .'' Well - perhaps the lyrics lose a little in translation. ''Romance'' waltzes pleasantly and slowly over the ears, and the faster material on ''Salute'' is appealing if undistinguished. Whether or not his music and lyrics shine every time, Lightfoot's tenor and guitar are welcome on my stereo.