It is also difficult to say when things started (Although styles as we know them today did not appear until the 90s) but the Lowrey MX1 was probably the first home instrument to have orchestrated backings (Although still called rhythms until the 90s) that bore some resemblance to what we know today. (Lowrey were always pioneers of easy play features)

Here is a review from around 1981 of the MX1 (And people complain arrangers are heavy) Review

Below is a recording from around the same time (Who knows without the pioneering work of Lowrey with the easy play feature set, things may have been totally different today)