Aviary's online music creator Roc has a large library of sounds to use in your creations. However, you can also record and create with your own custom sounds! Create beat box sounds, record alternate instruments, or just experiment with different sounds. To record a sound in Roc, open the option menu by clicking the gear button at the left corner of the track. Navigate to Sounds>Replace Sounds, which will let you open the sound recorder. After authorizing the application to use your mic, you can record custom sounds for your beats!