Hi Oberon,
Instantaneous Personal Magnetism is a good choice. You could also consider Personal Genius. It allows you to name your goal for each listening session, so your mind is prepared to hear the appropriate message.
I used Personal Genius for this purpose, and have noticed a measurable improvement not only in my singing ability, but also--and more importantly to me--a measurable increase in my comfort and confidence in singing. When I use this paraliminal, I feel as though I've sung professionally for decades, though I've never had that kind of actual singing experience.
Best wishes!
