All the onride music you hear is done with speakers and in-game music. These speakers can't be synced with the ride, otherwise it would've been better

I hope frontier will make an option to sync these speakers for music just like the effect-speakers
Hmmm... This is something I've been wrestling with myself. As the game stands at present, if you can chop the song into segments and load each segment as a separate custom music file, then you could hove a line of speakers each playing a sequential song segment upon being triggered, plus synching everything up like in one of those light shows. Which is pretty much analogous to hand-carving a phonograph record.
But before you can get to that painful job, there's the problem is chopping the song up into segments. Normal music formats don't like that. Maybe there's an audio editor for that. I don't know---haven't looked all that hard. But what I do know is that there's another, much more laborious method that will work if you're willing to invest the time. What you do is, get one of the freeware ABC-notation editors and type however much of the score you want in ABC notation, which is actually just a text file. Because this is a text file, you can chop it up no problem, however desired. Then there are other freewares that will convert the ABC to MID, and others that will convert MID to WAV which PC will accept. And some of the MID-WAV converters use soundscapes so you can actually make them sound OK. Anyway, after all this, you'll have all the segments of the song (in instrumental form, of course).
I've been pursuing this general scheme of ABC -> MID -> WAV to get my own songs into PC. It does work, and it would work for what you want. But it's a pain and I'm not entirely thrilled with the results. I'm just doing things this way because I already had the software for other purposes. But I'm getting really tempted to see what sort of audio editors are out there.