Wood privacy fence - planning over the top? Alternatives?

Since the relationship seems to be quite good, just address it openly. You have already asked several times in the past to lower the volume. In fact, it still bothers you much more often than the times you brought it up. You want to find a permanent solution. If giving up the music or significantly lowering the volume is not an option, only a wall for soundproofing would be possible.

The passive-aggressive reaction is out of the question anyway because I want my peace, and playing Rammstein at the neighbors to annoy them would 1. not contribute to improving our currently good relationship, and 2. annoy me more than the neighbors. ;) I will bring it up again in a personal conversation and have noticed that they have already turned the volume down compared to Father's Day. The fact is, it still bothers me. I also don't know if you can still call it room volume, since it is not played in one room and the sound can move completely unhindered against my house wall. Besides, we are disturbed by the bass thumping from the TV - in the living room, with windows closed and shutters down. It is still audible in addition to our TV. But I don't care, I would rather solve it at my own expense than cause the neighbors (whom we really like, which often gets lost in such a topic) permanent discomfort. What kind of wall would you suggest? From an aesthetic point of view, I would tend to brick / klinker stones. However, these are not exactly cheap at 30-40€ per m². We are also considering our terrace stones, which look quite nice from the side and cost only about 14€/m². However, this price probably refers to m² when laid on the ground. I don't know how expensive it would be for 1m² built, I would have to calculate it based on the size. I also don't know if you are simply allowed to use them for this purpose. That is practically repurposing.

Why not try a noise barrier for gardens in the terrace area

Try using a noise barrier wall for gardens in the terrace area

Gabion fence, at least 200 cm high.

Thought more of Kokowall and not the easiest one of it

Thought more about Kokowall and not the simplest version of it

I have also come across Kokowall. Our system would cost around €4000, but it would look nice and be exactly what we are looking for. I am wondering if something like that could be made cheaper by ourselves, for example with a rod mesh fence and panels made of insulating material, such as cork? Or what else would be suitable for that? What bothers me mainly are the bass frequencies (that is also something that can be heard through the walls in the house). Someone here in the forum said that for that I would especially need mass to mitigate it. So rather a wall/concrete/brick and mortar?

What bothers me primarily are the basses (that's also what can be heard through the walls in the house). Someone here in the forum said I mainly need mass to mitigate that. So rather a wall/concrete/brick and mortar?

Yes. The cheapest option would be a gabion wall. You can even build that yourself. Take at least 200 cm in height – if that seems too massive, you could also loosen up the wall a bit with laminated safety glass (VSG) elements in between or on top as a finishing touch – whether clear or satin is up to you.