Secondary dominants are chords that temporarily tonicize another chord in a song. They function like a V7 chord but resolve to chords other than the tonic, such as V7/II or V7/III. Secondary dominants contain a non-diatonic major third or minor seventh that creates tension and leads to resolution. The song "Don't Know Why" uses secondary dominants like Bb7 and D7 that resolve to Ebmaj7 and G7 respectively through tritone resolutions. Guide tone lines in the song outline these secondary dominants and their resolutions.