No additional chip needed. With the USB Serial chip, the only special thing programming does is it's got one of the unused lines on the usb serial chip, RTS IIR

No additional chip needed. With the USB Serial chip, the only special thing programming does is it's got one of the unused lines on the usb serial chip, RTS IIRC, hooked up to drive the reset pin low. The bootloader that the Arduino uses listens on the serial port for a magic number on bootup to enter into programming mode, no special chip needed. With the webaudio setup, I guess that's fair enough. For being absolutely foolproof being able to say to go to a specific webpage and then press play on tape is something we've been doing for a while. I personally prefer USB/Serial programming, but that's possibly just me having dealt with too many hand-me-down radios with scratchy headphone jacks over the years.