There's paid services like
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.
Other than that, you can browse site like
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or
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for packs.
You can also contact independent artists direcltyl, and they may often give you permission to use their music.
There's also free AI services like
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where you can make your own tracks and produce decent-quality music if you put in the effort. This last one technically doesn't let you use it for porn, but they're unlikely to find out unless you're publishing on Steam, and if you're publishing on Steam, you have the money to pay for you music.