I can't answer the question about backups, but I can provide some background on the Dropbox tracks.  Before the Community tab in the Sisyphus app was functioning, some of the earlier recipients of the table (mainly through the Kickstarter campaign) had learned about the track file structure and developed some of their own tracks.  The browser version of the app allowed uploading of track files from the computer directly to the table.  So in order to share tracks, some of us uploaded them through various methods (e.g., Dropbox, GitHub, etc.) to make them available for intrepid table owners.  Bruce then brought all of these under a single Dropbox location.

Now that the Webcenter/Community part of the Sisyphus interface is fully functional, the Dropbox archive is not really used.  But not all of the artists who contributed to the tracks previously provided through Dropbox have done so through Webcenter.  In my case, there may be a few tracks available I designed and shared in the Dropbox archive, but have not made available through the Community tab.  Now that I've got the track sharing figured out in the Webcenter interface, I intend to use that exclusively from now on.

I'm working on some ideas for new tracks but the kinds that I like to make are challenging to design, since each one is generated from a single mathematical formula.

@heropup - thanks for filling in the history of our Dropbox repo not being mirrored.

@john.hughan - I had to check with Micah, since my knowledge of hi-level repo admin (WebCenter and Community) is pretty superficial:

1. Tracks - all tracks (either shipped with the table or downloaded from the Sisyphus Community) exist remotely, so are retrievable.  The only exception would be if you create a track on your computer, upload it to your table, and delete it off the computer. (Using WebCenter, you can store any number of your original tracks, and choose whether any/all are shared. You can always retrieve your own tracks.)
2. Playlists - unfortunately at present, WebCenter cannot store your playlist info. As a work around, Micah suggests you can copy all the files in your table's /sisbot-server/sisbot/content folder. It includes all the tracks on your table as well as all your playlist info.

@heropup -- Thanks indeed for the background on Dropbox vs. Community!

@Bruce, I realized that resetting my table would not delete the tracks beyond any possibility of retrieval, but I just wondered if there was a way to back up the specific list of tracks that I had chosen to download to my table so that I could quickly get those (and only those) back onto my table.  It sounds like the workaround you provided will be perfect for that and the playlists, but going to that location returned a basic text page saying that it could not GET that location. Is SSH the appropriate mechanism for this?  If so, what are the default credentials?  Thanks very much!

And for Dropbox vs. WebCenter, will those repositories ever be "harmonized", or will the the tracks missing from the latter ever be pulled over from the former, since WebCenter seems to be the expected sharing/retrieval method now?  Initially I thought that the Community section was just pulling all available THR files from the public Dropbox folder on the backend, since many tracks were common to both, but evidently not.

@john.hughan - Just sent emailed the Pi's login creds (changed from default). The full location is home/pi/sisbot-server/sisbot/content. You can use SSH, or FTP (I find the later an easier interface).

WebCenter / Community harmonization - as I understand our current setup, they live on separate repos. Community is strictly for downloading community-shared tracks - whereas WebCenter is for composers - whether they share or not. You create a separate account for each. WebCenter allows us (admins) to make sure that shared tracks are a) playable, and b) don't break our TOS rules. But a composer can create and upload any track content they want if it's marked private (vs. public).  The Dropbox folder is now vestigial - but as you noted, still has tracks that haven't been migrated. Not every early composer has created a WebCenter account - but we'll eventually get around to putting them into the Community  (I got permission to share every track in the public Dropbox).

Makes perfect sense Bruce, and I received the email with the credentials. Also good to know that FTP is available, since that's a bit easier for me to work with on a Windows system compared to using SSH through PuttY. Thanks!

I recently had to re-image my SD card due to corruption.  It caused my table to no longer function (not even power up).  Happy to say the re-imaging worked, and now my table is functional again.  However, I had A LOT of extra tracks downloaded.  You say they exist remotely, so is it possible to get them all back?

@scott-piersma - Where did you download these tracks from? If it was the public Dropbox, they are still there. If from the Community (via our app), they also should still be available for dl.

@Bruce - I was hoping that a track by track download was my last resort, and that I could find them stored somewhere. Oh well, good thing we’re stuck at home. 

Now that I'm re-downloading all the tracks (both from the dropbox and app), none of them come with the preview images.  They all show the general Sisyphus logo.  When I get into the Advanced Settings and click the top bar 7 times to get into Table Settings, I see a button to Regenerate Images.  Mine is currently grey and says "Regenerating."  Any idea on how long this takes?