Singing combines speech and music – two activities common to most human cultures. It involves precise, coordinated control of breath, vocal folds, vocal tract, and their interactions. This chapter first introduces the interaction between laryngeal airflow and vocal fold vibration that produces voiced sounds. It then discusses laryngeal mechanisms or registers, and how nonlinearities in the larynx produce the harmonically rich voice spectrum. Acoustical properties of the vocal tract and its resonances filter the voice spectrum, but also affect vocal fold vibration. Finally, it discusses how singers adjust their tracts using resonance tuning to produce louder, more stable voice with less effort.