 " What You Waiting For ? " combines the genres of electropop , new wave , dance @-@ rock , and funk , and was composed in common time and in the key of G minor . It is written in verse @-@ chorus form , and its instrumentation derives from the guitar and electronic keyboard . The song opens with an emotional piano solo as a tribute to Stefani 's time with No Doubt . The verse begins at only 60 beats per minute and gradually slows , mixed with sounds of applause from the audience . A beat set at 138 BPM begins , and Stefani repeats the phrase " tick @-@ tock " , commonly interpreted as a reference to her maternal clock and the pressures she felt about producing the album . 
