Soundsets for Blofeld usually consist of a .mid file.

This has to be played back to Blofeld like a regular MIDI sequence. Most of the sound sets come with multiple files having the same name and “Bank A/B/C…”. This stands for the bank letter of the sound bank in Blofeld that will be overwritten with the new sound bank. Decide on which bank of your Blofeld the new sounds should be saved to and choose the corresponding file. These files contain the same soundset. You should just transmit one of those to Blofeld, otherwise the same soundset will be present on several banks of Blofeld. Blofeld has only eight banks from A to H, it’s not possible to add another one.

On mac OS, you can send a MIDI file easily by using the free tool “SysEx Librarian.” For Windows you can use “MIDI OX,” which is also free.

You also can send it with a DAW like Cubase, Logic… (This procedure won’t work with Ableton Live and Bitwig, as these DAWs don’t support Sysex data). Connect your Blofeld through USB or MIDI to your computer. Load the .mid file into a MIDI track of your DAW and play it back to your Blofeld. Reduce the playback speed to 80 bpm and activate transmission of Sysex data, if necessary.

Alternatively, you can use Spectre. Spectre is available in the download section at the end of the FAQ list. In Spectre, click on Audio/MIDI and select the MIDI out connection where Blofeld is attached to. Now click onto Upgrade… in the main window of Spectre and select, which .mid file you want to transmit.