It may appear I haven't been very active lately with news. It is for a reason. I want to make sure that MegaDrum is future proof and this is why I ported MegaDrum firmware to pic24 and pic32 MCUs awhile back, see http://www.megadrum.info/forums/viewtopic.php?f=3&t=447&start=0&hilit=pic32 for details. Last month I was getting to know ARM MCUs and as a result I've now ported MegaDrum firmware to an ARM core and specifically to STM32F103VBT6. Here is the picture of a working ARM prototype:
As you can see it is an SMD package so it is not easy to build for a not so advanced DIYer but when and if MegaDrum requires more power than Atmega can provide I already have a platform ready to switch to and continue development. No, don't worry, Atmega has still enough power to handle MegaDrum's requirements.