The KN7000 and KN2600 will only correctly 'address' standard SD Cards up to a capacity of 1G Byte. SD Cards up to 2 GByte can be used but the keyboards will ony 'see' them as a 1G Byte card. This is due to the addressing 'limit' of the KNxxxx operating system. What you have to recognise is that the KN7000 and KN2600, were produced before the advent of SDHC cards, so it is not surprising that their Operating System does not recognise these higher capacity cards, which use a totally different addressing protocol.

A 1 GByte addressing capacity is MORE than adequate, for storing 99 Technics Format song folders. Assuming that every folder contained 20 Song files - which will result in an average size of around 1.4 MByte per folder - even if all folders are full, this will only occupy around 139 MBytes of the available capacity. The remaining capacity could be used for other files such as MIDI and MP3 songs.

In short, the 1 GByte addressing capacity, which was inherent at the design stage of these keyboards, cannot really be considered a limitation. The fact that Standard SD cards are becoming scarce, is not the fault of the KNxxxx designers - or in fact designers of cameras or other equipment which use the original SD Cards.
I guess it's called 'Progress'...........