No. You do not own the music. Purchasing a license only allows you to use the music for your commercial project and the purpose specified in the license. That is different than ownership. We own all of the copyrights in and to the underlying composition and sound recording of every track.
You may not market the music as your own even if you add other instruments or a vocal to the music. Your Soundcritters license does NOT allow you to upload your project to YouTube’s Content ID system. Uploading Soundcritters music to Content ID will cause mistaken copyright claims for other users and for your future projects, and constitutes a violation of our licensing terms.