How do i make custom music assigned to a music disc?

 Well I have not yet made a music disk item, I did make a mob with custom sounds. When creating the mob I could pick sounds for the random sounds, & step sound & death sound... & pick from sounds in minecraft. As well as under Triggers I could find an action that plays a sound under world management by adding play __ at ...  & selecting an entry sound.  After I had sounds set to something & all the triggers made, I had to make some short sounds & convert them to a ogg file. I found an mp3 to ogg converter & some short sounds that fit my mob. Then I had to go to the Resources tab to add a sound under sound files & import ogg sound(s). Then I added the sound files to the mod & last I edited the mob & picked the custom sounds I had just added.  When u make a disk is it asking for u to pick a sound?  u can change the sound after but if u want a custom sound or image it is best to make or import it first on the resources.  Hope this helps.  I may come back when I try to make a music disk.