I assume the KN7000's audio (WAV, MP3, or?) files (recorded from the mic) are stored on the SD Memory card, right? As a vocalist, I want to be able to record & play back my vocals along with the midi sequences, so wondering 'how much' space is used when storing 'audio'. How many minutes of digital audio can be stored on a 128mg SD card vs 512mg card? I guess depending on the current price for a 512mg card, getting multiple 128mg cards might be a more economical alternative. Thanks - Scott