Music goldmines? New box sets by Jimi Hendrix, Joni Mitchell, Frank Zappa and more.

Music goldmines? New box sets by Jimi Hendrix, Joni Mitchell, Frank Zappa and more.

It’s been 40 years since Bob Dylan’s “Biograph” became the first CD box set to be released and there’s still gold to be mined, in some cases musically and most definitely financially. At least there is for Dylan and other veteran artists whose fans pay sometimes heady amounts for CD and vinyl box sets of both unreleased and previously released music. The demand has grown exponentially greater since 1985, much to the delight of those artists (and…