The plugin is a plugin. The Band-in-a-Box plugin doesn't communicate with other plugins like Rewire. However, there is a setting for the Band-in-a-Box plugin to sync to the DAW or to the plugin's MIDI soft synth. The screen shot below has the setting highlighted for the 2022 version 4 plugin.

As an alternative, why not (1) export the a wave file of the background music from Cubase. Then (2) use Band-in-a-Box's Audio Chord Wizard, or ACW for short, to create a tempo map and chord chart inside Band-in-a-Box. Then (3) create melody and solo tracks. Finally, (4) export melody and solo audio files back into Cubase if you desire.

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2022 V4 Plugin sync to DAW setting.

Jim Fogle - 2026 BiaB (Build 1217) RB (Build 4) - Ultra+ PAK
DAWs: Cakewalk Sonar - Standalone: Zoom MRS-8
Desktop: i7 Win 11, 12GB ram 256GB SSD, 4 TB HDD
Music at: https://fogle622.wix.com/fogle622-audio-home