Try this article, it will answer your question along with giving you a concise and accurate definition of what meditation is and how to practice meditation. There are a large number of different practices being called meditation today, but most of them create more activity in the mind. They have their own effect, but the real goal of meditation is to bring us more and more to the experience of our true selves. The article has been written by an enlightened person who is in this experience. You can find further information on this on the same site, including guided meditation videos, but the article contains enough info to answer your question.

Update (Sep 5, 2019): Another video from the same site can give you understanding about creating silence vs creating more activity in the mind in terms of spiritual awakening. The video contains direct information about how you can measure how awakened you are spiritually and the process to awaken spiritually.

Update 2 (Oct 27, 2019): As you can understand by studying the above resources, meditation is a state of focused awareness. Certain objects such as the breath and the energy of love in our heart carries us to the depth of our being and we focus on one of these during meditation. This is a practice of focusing our attention to an already existing object, not imagination.

You can try to imagine fantasies in your mind but if your attention is not moving to the depth of yourself, you will just be imagining fantasies. People are known to focus on thoughts and philosophies and spend lifetimes without going to the depth of themselves. This is because their focus remains on the surface level of their minds. Listening to drumming can also dull your mind in the sense that it is repetitive and keeps your attention on your senses by repeatedly stimulating them. This is different than using meditation bells that ring from time to time to refocus our attention to the object of meditation. While listening to drumming or music can bring some order to a wild mind initially, listening to constant drumming or listening to music will be distracting when going deeper in meditation in my opinion. The purpose is to remain focused on the object of the meditation and specific objects such as the breath and the energy of Divine Love are chosen because both are connected to and coming from the very depth of ourselves.

About the tunnel and darkness, what I can say is, with the way your attention is keeping stuck on the surface level of your mind due to the way you meditate, you are unable to perceive/home in to the energy of Divine Love within your heart. In the darkness, as the space, you must learn to focus to the depth of yourself to this energy of life that is one with you. One aspect of you is the formless Awareness, another is the Divine Love. When formless Awareness is stuck on a surface level of the mind without experiencing the Divine Love, it will feel like a desert. That is why you must practice a genuine meditation that is recommended by an enlightened teacher. Visualization practices can have the effect of creating some concentration and discipline, but if the teacher is not enlightened, he can’t teach you to go to the depth of yourself, because they have not traversed the way themselves. I am a student on the way to achieve this with some deep glimpses into it, and I can tell that you are stuck in the surface level, and the resources I had given links to above are coming from a fully enlightened person and can definitely help you if you study them.