Trance and lucid dreams

Hello, I was needing some info pertaining to trance clarified. I find trance important because if one can enter this state Lucid dreams are a piece of cake. Infact one of my first experiences with trance was awakening in a black void and watching a dream literally form in front of me.

The problem is the difference between Trance and simply being in theta or alpha. So I was told that trance is when you are conscious and your brain is in alpha- theta (or delta but I wont discuss that yet) And it would seem to make sense from my previously mentioned experience. I was in deep sleep and arose from it into wakefulness in a black void, (like the blackness behind my eyes became a large room) I had no sense of my physical body, and a dream was forming which indicates theta but I was HYPER aware.
Meanwhile, I can try to meditate, and reach a daydreaming- dozing off state which would indicate alpha then theta but the black room does not appear… I do not feel any change except sleepiness, and my mind trails off… So the question is, what is the difference? What am I not doing in the latter example?
Thank you for your time in advance!