Interference from another meditation technique in my vipassana meditation

In my 20's(I am now 55) I practiced light and sound meditation for 7 years. When I am doing vipassana which I started in March this year (having not meditated for 25 years) I get the 'sound' mainly engulfing me and it is very blissful I must say. I might also get a huge gushing out of the top of my head and that draws me in to. These moments can feel very blissful. I made a conscious effort to ignore these events and have mainly succeeded but sometimes I still get sucked in because I want to or as a 'treat'. What effect will this have on my vipassana? Is it safe to allot some time for that meditation outside of the vipassana meditation? Is it ok toward the end of a sitting to let myself focus on the sound instead? Should I let the sound buzz through me at the same time I focus on my body parts?