▁an ▁Italian ▁composer ▁of ▁modern ▁classical ▁music , ▁conduct or , ▁and ▁teacher . ▁He ▁is ▁considered ▁one ▁of ▁the ▁most ▁influ ential ▁Italian ▁compos ers ▁of ▁the ▁tw enti eth ▁century . ▁ ▁Life ▁Pet rass i ▁was ▁born ▁at ▁Zag ar olo , ▁near ▁Rome . ▁At ▁the ▁age ▁of ▁ 1 5 ▁he ▁began ▁to ▁work ▁at ▁a ▁music ▁shop ▁to ▁supply ▁his ▁family ' s ▁financial ▁needs , ▁and ▁became ▁fasc in ated ▁by ▁music . ▁In ▁ 1 9 2 8 , ▁he ▁entered ▁the ▁Santa ▁Cec ilia ▁Conserv atory ▁in ▁Rome ▁to ▁study ▁organ ▁and ▁composition . ▁In ▁ 1 9 3 4 , ▁composer ▁Alfred o ▁Cas ella ▁conducted ▁Pet rass i ' s ▁Part ita ▁for ▁or chestra ▁at ▁the ▁I SC M ▁festival ▁in ▁Amsterdam . ▁ ▁Later , ▁Pet rass i ▁became ▁musical ▁director ▁of ▁the ▁opera ▁house ▁La ▁Fen ice , ▁and ▁from ▁ 1 9 5 9 ▁taught ▁composition ▁at ▁the ▁Santa ▁Cec ilia ▁Conserv atory ▁and ▁at ▁the ▁Sal zburg ▁Moz arte um . ▁Pet rass i ▁had ▁many ▁famous ▁students , ▁including ▁Franco ▁Don at oni , ▁Ald o ▁Clement i , ▁Corn el ius ▁Car de w , ▁En nio ▁Mor ric one , ▁Karl ▁K orte , ▁Bor is ▁Por ena , ▁Norm a ▁Be ec ro ft , ▁Mario ▁Bert onc ini , ▁Ern esto ▁Rub in ▁de ▁Cer vin , ▁Eric ▁Sal z man , ▁Kenneth ▁Le ight on , ▁Peter ▁Max well ▁Dav ies