I've witnessed the development of auto-accompaniment instruments beginning with a Yamaha Electone in 1985 via Gem WS 2 in 1991 to BK-7m and BK-9, a span of 30 years, too. But I also know that auditive perception is changing. What sounded spectacular in 1991 sounds cheesy nowadays, so Tyros 4 sounds won't be good forever.