, ▁piano , ▁and ▁drum ▁programming ▁( track ▁ 1 1 ) ▁ ▁Alex ▁V eng uer ▁—   ass istant ▁engineer ▁( track ▁ 1 0 ) ▁ ▁Patrick ▁Warren ▁— ▁key boards ▁( tra cks ▁ 6 , ▁ 8 , ▁ 1 2 ) ▁ ▁K any e ▁West ▁— ▁producer ▁( tra cks ▁ 2 , ▁ 1 2 ) ▁ ▁will . i . am ▁— ▁producer ▁and ▁engineer ▁( tra cks ▁ 1 , ▁ 5 , ▁ 7 , ▁ 1 3 ), ▁drums ▁( 1 , ▁ 5 , ▁ 7 ), ▁bass ▁( 7 ), ▁drum ▁programming ▁( 1 3 ) ▁ ▁K eb bi ▁Williams ▁— ▁horn s ▁( track ▁ 6 ) ▁ ▁Steve ▁William son ▁— ▁clar inet ▁( track ▁ 1 3 ) ▁ ▁Jess y ca ▁Wilson ▁— ▁background ▁vocals ▁( tra cks ▁ 1 , ▁ 2 , ▁ 5 - 7 , ▁ 9 , ▁ 1 1 - 1 3 ), ▁ad - lib ▁vocals ▁( 7 ) ▁ ▁Mate uz ▁Wol ski ▁— ▁viol in ▁( tra cks ▁ 4 , ▁ 6 ) ▁ ▁Sh elly ▁Wood worth ▁— ▁ob oe ▁( track ▁ 1 3 ) ▁ ▁Sh aron ▁Yam ada ▁— ▁viol in ▁( tra cks ▁ 4 , ▁ 6 , ▁ 1 0 , ▁ 1 3 ) ▁ ▁Jung ▁Sun ▁Y oo ▁— ▁viol in ▁( tra cks ▁ 4 , ▁ 6 ) ▁ ▁Ch arts ▁ ▁Week