Playsound only play some sounds

The play sounds command only plays some of the default sounds and none of my customs sounds. I see this had been mentioned before but not sorted. I have read and watched several tutorials on how to get it working but none work. I did have it working under 1.6.4 of which i have set up several command blocks setup to play various sounds, which continue to work under 1.6.4 but not under 1.7.2. I tried the editing of the sounds.json file but it keeps reverting back to the unedited version once i start the game.