No need to require space age mod.

local planet = nil
if data.raw["planet"]["aquilo"] then
  planet = "aquilo"
elseif data.raw["planet"]["nauvis"] then
  planet = "nauvis"
end

data:extend(
{
  {
    type = "ambient-sound",
    name = "FFF Aquilo Teaser OST",
    track_type = "main-track",
    planet = planet,
    sound =
    {
      filename = "__fff-aquilo-ost__/fff-406-undisclosed.ogg",
      volume = 0.7
    }
  }
})

if you want people to have DLC just put:

"space_travel_required": true,

inside info.json

The.... entire point of this mod was to add a track to Aquilo's soundtrack pool specifically, as I felt it was sorely missing during my playthrough (I'd speculated in the months leading up to 2.0's release that it was going to be a track on whatever the "cold planet" was as hinted in the christmas teaser image). I do appreciate the Lua advice- but I also see literally zero point to drop the Space Age dependancy when it should contextually only ever play inside of a Space Age planet. Even if I add an option later down the line to make it play on Gleba instead (the other possibility for where the track could've come from- but IMO it doesn't feel appropriate), that would still necessitate Space Age.

some player like to play without planet in space age like mod such as https://mods.factorio.com/mod/EverythingOnNauvis. Or just also me who just wanted more music on vanilla nauvis, or whatever reason. There is no need to limit the music to only space age + aquilo. but whatever guess I will do it myself then.

To do that would be breaching copyright and violating the license of Space Age and Factorio. If you want the Space Age Music, purchase the DLC otherwise you're stealing.

To do that would be breaching copyright and violating the license of Space Age and Factorio. If you want the Space Age Music, purchase the DLC otherwise you're stealing.

not at all, read again my first message

if you want people to have DLC just put:

"space_travel_required": true,

inside info.json

You miss understand my point, my proposed code will actually show this mod is a space age dlc mod, contrary to current version of this mod.

You can also read my opinion about this on one of my own mod https://mods.factorio.com/mod/TurboBelt/discussion/694eeb6c84cc39532dec8df2

You totally miss read what I have said and what the code do.

I didn't notice it wasn't marked as a "Space Age Mod"! Thank you for bringing that to my attention, I've added that bit to the json and pushed an update out.

I understand the intention behind your rationale, but...

some player like to play without planet in space age like mod such as https://mods.factorio.com/mod/EverythingOnNauvis

...that mod also requires space-age as a dependency? Am I misunderstanding something?

Also- would your code specifically only put the track on Nauvis if Aquilo didn't exist in a save, or would it play on both Nauvis and Aquilo? I'm not really versed enough in Lua to know what that if/else really entails.

only aquilo if aquilo exist, and nauvis is a fallback, that not complicated code and I get it if you don't want to do it. I'm mean that your mod, I just didn't agree with the reasoning.

I honestly don't mind doing it that much- I just wasn't sure what the rationale behind such a change would be, and I'm still not sure if you're asking just for the code change or if you actually wanted the space-age dependancy removed outright? I'm trying to understand the reasoning given it doesn't seem like the other mods referenced do this.