Pioneer's abysmal (and discontinued) MixTrax software, for preparing music on USB sticks for use with speed control on the
Steez boombox in dance classes. Copying the database from an existing stick lets new ones work.
MixTrax (which was last updated in ?2015 and is now only available from third-party app finding sites) installs but refuses to load on macOS 13 Ventura, but still opens on my mother's old computer, which is running 10.11 El Capitan. When you plug a USB drive in, it gets detected, with a dialog box asking for a name for the drive and the mysterious commands of 'Yes' or 'No' (presumably for confirming or cancelling the change of name from 'Removable Disk 2' or whatever the default is?). But it doesn't show up in the sidebar to sync music to.
Drives you've already used will show up in the sidebar. But this isn't ideal, as the only way of adding music to one is to overwrite all the current music with whatever playlists you tick. We're afraid of messing up the process and losing access to the sticks we already have set up.
MixTrax creates a folder on the root of the drive with its database of music files (still usable elsewhere but named as four-digit numbers) and the extra data it uses for speeding up and slowing down tracks independent of pitch. In desperation I tried duplicating a known working drive's contents, and it turns out that this is enough to 'bless' the drive so it is syncable. Even if the new drive is a different capacity. So now we have a mini-playlist we can prime additional USB drives with.
Over a decade after its release, I would not recommend this boombox to anyone - a tablet with Amazing Slow Downer paired with a bluetooth speaker will almost certainly work better in class, and will involve significantly less headache in setting up. It does meet my mother's particular use case for playing music at dance classes - the remote is compact but has buttons for FF/RW & volume control & speed control & track skipping, which I'm struggling to replicate with a keyboard-in-disguise media remote, and it's bulky enough that at public performances it's less likely someone will just walk off with your tech. If you absolutely need a boombox, it would be better to stick to the previous popular option of getting Portogram's hacked JVC CD boombox with a physical speed knob (even though this does change the pitch at the same time). That still has an headphone jack input you can plug your iPad into for your digital collection.