Is it counter productive to accumulate a lot of ideas while meditating?

Accumulating ideas is what happens when we meditate. When we distance ourselves from the mind, we can watch these ideas in a detached way. For that we have to step back from all the influences inside our mind. When you have reached a place within where you can be quiet, then you can observe these voices to see what they are. Watch them in detachment. If you know Buddha’s teaching on not‐self it will be easier for you to step back and do the watching. Not only ideas but feelings of pleasure and pain too will come and go.

Another kind of ideas is perceptions, or thought‐ constructs. You can observe these too, to see the influence they have over the mind. Then you will know what type of ideas to encourage, and what to get rid of. Again if you know the Dhamma it helps. Dhamma contains all sorts of useful and encouraging ideas. You can broaden on the ideas of loving kindness for example. You can start with goodwill for yourself, then expand into goodwill for other people etc.

What has to be gotten rid of are the burdensome ideas - the burdensome notions the mind, Such ideas will make you react this way, to think that way. Once you identify them, you can let go of them. You do not have to entertain ideas of greed or anger that come in to the mind. Also never allow lustful or angry or cruel ideas to arise within you. With earnest effort, you can straighten out any crooked and bent and shifty ideas. Thanissaro Bhilkku once had the following to say about ideas:

”We hold on to ideas even though they have proven themselves again and again and again that they don’t work. It’s like that famous story about Nasruden eating a whole bushel full of peppers and crying. Someone asked him, “Why do you keep eating peppers when they make you cry?” And he responded, “Because I’m looking for the sweet one.” You may have some ideas about what should work, but when you find that they don’t, you drop them. You’re not attached to them. “

I looked up Muse Brain Sensing Headband and have to say that you cannot practice Buddhist meditation while using such a device for at least two reasons:

1. You should always try to be as secluded from sense impressions as possible (in formal meditation). Listening to sounds or music while sitting is counterproductive and not a Buddhist style of meditation.
2. As I understand it this device generates pleasant sounds when it senses less movement in the head (not in the mind!) and unpleasant sounds when the activity in the head increases. This is problematic! You're reinforcing judgement, thinking it is good to have a calm state of mind, bad to have an agitated state of mind. And also mixing up bodily and mental sensations (by mistaking the activity in your brain with the activity in your mind).

Since you asked about accumulating ideas, I guess that you don't have a clear and comprehensive instruction to follow. And since you asked this question on the Buddhism Stackexchange, you'll get the Buddhist explanation of meditation :). In Buddhism, the meaning of the word 'meditation' may differ from what you associate with it. A common misunderstanding is that you practice meditation in order to get calm. You don't. You practice in order to get wisdom. This can be done by using a calm mind, but only as a means. The following is a good, practical instruction based on the original Buddhist teachings (over 2500 years of people practicing it has proven it works): How to meditate.

Talking from a Zen perspective and Zazen meditation, one should just sit and stay with whatever comes up, and accept without judgment whatever rises in consciousness. Having a measure of how good or bad your mental state is, is judging what is coming up in the moment, so not supportive of Zazen.

Also as someone has mentioned and related to what I just said before, judging your mental state will lead to clinging to "good states of mind" and aversion of "bad states of mind" which will lead to suffering, see the 2nd Noble truth:

Dukkha, and repeated life in this world, arises with taṇhā, "thirst," craving for and clinging to these impermanent states and things. This craving and clinging produces karma which leads to renewed becoming, keeping us trapped in rebirth and renewed dissatisfaction

Citation from Wikipedia

About accumulating ideas, in Zazen the invitation is be aware of thoughts but not to engage with them and let them pass,so I believe there is nothing wrong with jotting them down after the session, some people even keep a log of notes, etc to discuss with the teacher.

Of course, there is nothing wrong with accumulating ideas, especially if they turn out to be useful. And if the head band helps you do that, why not use it? But there can be no doubt that you are not practicing Buddhist mindfulness meditation as it is described in the Satipatthana Sutta. Indeed, the meditation you describe prevents mindfulness from doing its job. I have just published a book called "How Mindfulness Meditation Works". It will be available in a month or so.

There are two types of meditation available in Buddhism. Samatha and Vipassana.

In Samatha, you should concentrate your mind into one target sense. The target sense can be inhale and exhale witch is popular as Anapanasathi. There are more Samatha meditation methods which are targeting difference target senses. Kasina meditation and Asuba meditation are some of them. There you continually get that target sense into mind without allowing any idea, sense or feeling other than that. Then you will feel your mind become more powerful and very high state of calmness. actually Samatha is like sharpening your weapons against a war.

As Buddhists, our main intention is to attain Nibbana. So after performing Samatha we look at the uncertainty of the body and mind. Here what we are doing is not generating ideas. but perform root cause analysis on uncertainty of body and mind. actually wipassana is like use your weapons against enemy.

you cannot get good results if you are not following sila, at least five precepts. My friend, Use five precepts not Headbands.