I recorded a long and important voice-memo on my old iPhone which is not synced anymore to any iTunes. I wanted to retrieve the memo using the advice here, however choosing Sync Music in iTunes brought up this warning:

I tried to click Sync Music and the capacity bar at the bottom indeed indicated that all music, and presumably the voice memos too, would be deleted next time I sync the iPhone (the blue Audio bar was completely gone). I immediately reverted.
How can I retrieve the voice memos?
The other options in the question linked above include:
- DropVox - which costs money and forces me to have a DropBox account
- Macroplant iExplorer - which is a freeware that doesn't work for me