Mercury 's vocals ranged over three octaves in Innuendo .
`` Stylistically , Innuendo is in some sense a return to Queen 's roots , with its harder rock sound , complex musical composition ( title track ) , psychedelic effects ( `` '' I 'm Going Slightly Mad '' '' ) , and somewhat weakened vocals from Mercury ranging over three octaves ( F2-A5 ) . ''
Innuendo -LRB-album-RRB-