BlobBuilder enables developers to construct files without having to upload and download any data to their server. File construction can take place entirely on the client.
In this demo, as you press the piano keys, two files are being constructed. A music file is created by appending mp3 files of individual notes. A sheet music svg file is created from the svg content of the page. As you add notes to your composition you'll see the file sizes changing. When you are finished with your composition, you can download the music mp3 file or sheet music svg file.