for me maturity is when you go in a more technical way of doing music...
i think maturity is not only in the music itself but also to the band members...
example, bagohan palang kayo as a band, so plug and play kau and wala ng adjustments or tuning, isip nu lang makatugtog, bahala na, parang bata ang dating... BUT when u grow mature, namimili na tau ng amps, fine tuning na tau sa effects natin, ung way of composing riffs, lyrics, or drum line pinaplano na talaga... i think u get the point...
and also sa members, mature na din magisip...
metal head kasi ako but ive experienced that... no comment sa jazz pero gusto ko un pang pakalma...
about shifting wala naman probs sa maturity, but iiba na naman enviromnment mo kasi from rock to jazz... so adjust ka... meron na bang rock star nag shift into jazz?