Musicians are looking for new ways to make their shows more interactive and to connect with fans. And Sonic Notify thinks it's got just the technology to do so. With that in mind, the startup raised $4.25 million and has struck a partnership with Interscope Records, which will make its technology more widely available to musicians on that label. Sonic Notify uses soundwaves which are inaudible to the human ear to transmit signals to mobile apps that have its technology embedded.