I'm sorry but the volume workaround wouldn't be easy to do consistently, in real time. Stopping the accompaniment manually with a foot pedal would be a better solution, but not something I would want to do every few measures.
One weakness of arrangers is that once you've activated the accompaniment it goes on relentlessly. It can make music sound, "arrangerish." Sync stop is great for dramatic pauses. It emphasizes the fact that you are producing "live" inputs (i.e., playing), and not just running a sequenced backing track. Some arrangers have a "break/fill" that could be used for this purpose. I can't remember if the GO:Keys has one.
Activating sync stop is also a great workaround for pieces that have a change in the time signature- another inconvenient truth that robotic arranger accompaniments don't deal with very well. Of course the Sync Stop trick only works with styles that lack a strong rhythm, such as Yamaha's "free play" styles and Casio's "string quartet." These coincidentally are great for traditional worship music.
I've been playing arrangers for a long time, going all the way back to home organ days. I consider sync stop an essential feature, and what's more, it shouldn't have been dropped in the first place. The board has (a somewhat poor implementation of) sync start; it seems like a no-brainer to add the complementary function.
I know that Roland Europe folded about a decade ago, and Roland's last full-featured arranger, the E-A7 was developed in Japan. I'm not sure if the same team is working on the GO:Keys 5 but it has many arranger-like features. Even before the demise of Roland Europe, Roland had a bad habit of dropping some features and adding others in the change-over from one model to the next.
I'm not willing to overlook the lack of sync stop so easily, and without it IMO the Casio CT-S500 is a better arranger in this price and weight class.
