It took me a while to figure it out but I did, although for a different purpose (to display the IP address of the current wifi connection).
The way I did it was to use the Minimalistic Text task, edit the configuration so that you enter a dedicated variable name not used for anything else eg %SONG_NAME next to "Variable name" and the value eg %SONG into "Variable content". You obviously will have had to get your song title into %SONG somehow and I haven't investigated how to do that.
Then in your Minimalistic Text widget, you will need a "Locale variable" entry under the LAYOUT tab into which you will need to enter %SONG_NAME into the "Variable name" field.
This took me a bit of faffing about to get to work but it does seem to work perfectly now and Minimalistic Text does notice when the variable value changes and updates the widget appropriately.
