12decode

In addition to the outdated sysex documentation, at least in firmware 1.15, a protocol for the multimode is implemented

A wavetable dump is used to transfer wavetable data to the Blofeld. Each wavetable is transferred as 64 consecutive wave dumps.

Convert a 21 bit signed integer (provided in three 7-bit characters) into a 32 bit signed integer

http://stackoverflow.com/questions/11704309/how-to-build-a-negative-32-bit-integer-from-bytes-without-a-range-check-error

          uint32 sample =
          (sysex[kWavetableDataOffset + index * 3 + 0] << 14) |
          (sysex[kWavetableDataOffset + index * 3 + 1] << 7) |
          (sysex[kWavetableDataOffset + index * 3 + 2] << 0);
          
          if (sample &  0x00100000) {
              sample |= 0xfff00000;
          }
          
          curWavetable.data[wave][index] = (int)sample;