There are many Apple-1 emulators available. My personal preference is OpenEmulator for OS X. Open Emulator is able to use and create audio files that work with the real hardware. It also let’s you emulate the Apple ][ and Apple-1 workalikes like the Replica-1.
MESS is a general emulator that has the option to emulate the Apple-1. MESS is the most popular vintage computer emulator and is available for Windows, OS X and Linux.