scripts/copyright

Have a play i would like to post, but part of the stage directions are as to what music is playing in the background or can be heard, do i reference this by just naming song and artist or is it copyright to even name them? also, at one point, character sings along to song - can i put the words 'sing along' within their speech...without it being plagiarism or accused of? Hope this makes sense!! Ta, Mikey