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But suppose I add album art( or whatever) to a song while listening to the Mac. Would that be reflected in the pc j river the next time it is used?
Would I have to maintain all of the stuff (lyrics, album art, rating). Etc. TWICE?. That is I want to avoid if possible. It becomes a Herculean struggle at some point with large libraries. I also am unclear how the Mac version can save info to the FLAC file on an NTFS drive.
As you've written, Macs/OSX can read NTFS drives natively, however, they cannot write to an NTFS drive natively.
However, there are a couple of third-party (for pay) add-ons for OSX that allow it to write to an NTFS drive, discussed in the previous posts (namely Tuxera and Paragon programs).
There is also the exFAT format available on both OSX and newer Windows systems, which is cross-platform compatible and allows for a large number of files and larger (than FAT) file sizes. After investigating Tuxera and Paragon drivers, I use exFAT for PC <--> Mac compatibility.
So first you need to decide on a disk system that is compatible. You either format a drive with exFAT, or buy one of the additional NTFS programs for OSX and format with NTFS (there are even free versions, but they're limited in some ways, and I haven't bothered with them).
Next you need to decide where your "primary library" will be. Since Windows is stable and fully featured, and Mac is still in Alpha and just staring, for me that's a non-issue: Windows is where I will organize and tag; Mac is where I will mostly actually play
Next you copy the music files that you've tagged already in MC Windows. Plug it into the Mac, and import the songs.
Right now, with the alpha driver, the tags you've added in Windows will be there in the Mac library on import, though I haven't checked ratings or lyrics yet.
Cover art is a different story right now (an alpha statement I'm pretty sure). If the cover art is in the actual file, or in the directory of the album, then it will import no problem. Ideally, you could copy over your cover art directory from Windows to the Mac and find anything missing that way; I've found that doesn't quite work yet, so I've filled the occasional gap on the Mac version itself (from the internet or from a file, manually).
So the net of this process is this: I do all my tagging and organizing in the full-featured version of MC for Windows, then I always copy the data to the Mac and re-import. Works very well so far. Any tag changes / cover art changes I make on the Mac version will work on the Mac, but since I'm always copying from PC --> Mac means those changes will be lost. As I hinted above, as long as the Mac version is alpha, I'm never going to re-import those files back to the Windows PC.
Once MC is feature-complete (in beta, effectively), I will still use the same workflow as above, except I will import
only the changes I make on the Windows library to MC Mac (unless there's a compelling reason, like a code regression, to re-import the whole library again).
Once the Mac version stable, and is equivalent to the Windows version (for things like UPnP and maybe even video--hey, I can hope!), I will use the Mac version as the primary version and use the Windows system only as as a backup
That's the plan, anyway... you know what they say about the best laid plans, right?