A "captcha" is an added security measure that asks you to complete a short written ‘test’ to confirm that you are not a robot. We introduced this as a security measure to protect our users’ accounts from potential security breaches. 

If you are regularly signing in and out of your account on the same day, we're probably going to ask you to fill this out for us. To avoid getting it so often, we suggest keeping yourself signed in to your account. 
 

I need to sign into multiple accounts!

If you care for multiple accounts on SoundCloud, we recommend using incognito windows or multiple browsers for each profile. This helps reduce the captcha requests.