Presuming you meant "_GRVFLK2" (the initial underscore tells us it's a Realtrack versus MIDI style), there are no C/D parts associated with that style. Or are you creating your own by selecting another style for C/D.

All styles come with A and B part markers; others are created already defined with additional part markers (called Multi-styles), but most aren't. You can create your own multi-styles.

Not sure what you did in your song; the style played fine on my system. You shouldn't have to restart BIAB to play your songs (although after a long session, you might need to).

Maybe try resetting BIAB to factory defaults and see if that fixes it.

John

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