Custom Music Disc Does not create RedStone Signal When Played

Hi there-

we've successfully made our own music discs, but just discovered that they don't seem to generate any redstone signal when they're played- e.g. a comparator connected to a lamp doesn't light up.

When a built in music disc is played, the lamp lights as expected.

Did we miss a setting in MCreator?

Is there some custom code that needs to be added? If yes, what is it, and on which trigger should it be added? :-)

Thanks in advance!