Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
WaveShop - Open source audio editor
Adobe Audition - Mix, edit, and create audio content in Adobe Audition CC with a comprehensive toolset that includes multitrack, waveform, and spectral display.
TwistedWave - TwistedWave is one of the unique audio editors that allow you to edit your music file online without any installation.
GarageBand - GarageBand is a fully equipped music creation studio for Mac
Logic Pro X - Music production.