I’m not sure if this is exactly what you’re after, but perhaps it will give you some ideas. This would go in the File Naming script section. Warning, this is untested code.
$noop( Set a new _genre tag with default value if %genre% is empty. )
$set(_genre,$if2(%genre%,Unknown Genre))
$noop( Create a testing tag for year. )
$set(_testYear,$left($if2(%originaldate%,%originalyear%,%date%,0000),4))
$noop( Set a new _yearRange tag based on the year )
$noop( First check for unknown year. )
$if($eq(%_testYear%,0000),$set(_yearRange,Unknown Year))
$noop( Now do specific year ranges. Add or adjust ranges as required. )
$if($and($gt(%_testYear%,0000),$lt(%_testYear%,1960)),$set(_yearRange,-1959))
$if($and($gte(%_testYear%,1960),$lte(%_testYear%,1969)),$set(_yearRange,1960-1969))
$if($and($gte(%_testYear%,1970),$lte(%_testYear%,1979)),$set(_yearRange,1970-1979))
$if($and($gte(%_testYear%,1980),$lte(%_testYear%,1989)),$set(_yearRange,1980-1989))
$if($and($gte(%_testYear%,1990),$lte(%_testYear%,1999)),$set(_yearRange,1990-1999))
$if($and($gte(%_testYear%,2000),$lte(%_testYear%,2009)),$set(_yearRange,2000-2009))
$if($and($gte(%_testYear%,2010),$lte(%_testYear%,2013)),$set(_yearRange,2010-2013))
$if($and($gte(%_testYear%,2014),$lte(%_testYear%,2016)),$set(_yearRange,2014-2016))
$if($and($gte(%_testYear%,2017),$lte(%_testYear%,2018)),$set(_yearRange,2017-2018))
$if($and($gte(%_testYear%,2019),$lte(%_testYear%,2020)),$set(_yearRange,2019-2020))
$if($gt(%_testYear%,2020),$set(_yearRange,2020-))
$noop( Now build your naming string using the temporary tags. )
%_genre%/[%_yearRange%]/%artist% - %title%
Please let me know if I’ve misunderstood and you’re wanting something different.
EDIT: Added missing percent signs around _testYear tag when testing.