The way I understand it, going by the upakiesa sutta at MN128, the geometric figures are the forms “rupa” and the light is the obhasa mentioned. And just like the sutta, they can occur independent of each other, so you can see the forms in grayscale without much light, or there can be just an illumination which blots out the forms. I believe the light aspect is more useful component as I would feel happier and more excited with the presence of light and when only the forms were present I would feel impatience for them to turn into something more exciting. Probably the perception of light is solely the light aspect which dispels sloth and torpor and when it was strong I had more energy and as previously mentioned used it to contemplate body parts with better accuracy.
However according to the dark retreat documents which I read, color visions were supposed to arrive eventually but for me they rarely did probably due to wrong practice.
Also, I believe the vision of light and forms in the upakilesa sutta is to do with the development of the divine sight as a psychic power and what I perceived was just the slightest of tasters, due to a lack of power in my mind.
Also of interest here are the eight bases of transcendence and the eight liberations from MN77 and other places. I believe these rarely read and discussed frameworks are where access concentration (upacara samadhi) is described in the suttas.
This seems to me the ‘lived experience’ of mind free from sloth and torpor- a brightly aware and energized mind. It will be experienced as light- like sunlight off a polished metallic surface.
I use sound (music) to rouse me from sloth and torpor, especially when driving around. Recently I have tried to use meditation music/sounds to calm the mind, to relive stress at the end of a long hard day. Chanting, though somewhat different, can be used to concentrate the mind. Music can be uplifting as well, when feeling low. It can be used as a pleasurable distraction when caught up in negative thinking. Singing lullaby’s to my kids can help develop metta. Music can be an object of focus, especially with minimal vocals and more drum and bass.
Good, doing the same thing, and when driving I have a Buddha-rupa placed sitting facing forward on top of the dashboard, and use it for centering and anchoring awareness, to gain a sense of the world moving and mind sitting unmoved, let the landscape pass right thru “us”
Had a marvelous walking meditation in the city (4 hours), -walking aimlessly, while listening to the last album of David Bowie, and what a rush and uplift - and it’s an exquisite Grand Finali from dear David
I love asubha, and death and dying, but I agree with those who steer away from stuff like that - depressions and those aspect’s of the training is maybe not a good idea
I was into listening to music in my younger days, many lonly days just listening and listening, but now i find I can harvest quite a bit and use it in this practice, because the listening skills or talent has been trained for many years before and now that ability is of great use
So its important to choose wisely!