I thought I heared that combining several stops wich have combined frequencies these flow together and do not sound well separate.
Is there a way to prevent this?
At the level of the soundfont f.e.: combine several instruments in one preset, or combine sevaral samples in one instrument
or before adding samples to a soundfont: mix each note using audcity, reaper etc.
If I understand your post correctly, you are describing the problem where harmonics of one note “add” with the harmonics of other notes sounded simultaneously, with the result that the combined sound is either louder than it should be, or softer than it should be. (I think the latter effect is more of a problem, because the harmonic can disappear entirely! We call this “cancellation”. It can even happen with actual pipes, but is more noticeable with electronic instruments where lots of sounds are summed in the one audio channel.)
I think that the provision of presets which carry a number of stops combined together is a correct “intuitive” attempt to avoid the behaviour, but I don’t think that your suggestion of combining the sounds in a soundfont editor beforehand (presumably to create special new samples) will actually avoid it. If you want to combine the sounds in the way you seem to suggest, you would need to combine them in AIR, using a separate audio channel (and amplifier/loudspeaker) for each note, then play them together and record the result with a microphone, making sure that there are no passing aeroplanes or loud traffic. :-) This method will reduce the problem, but not overcome it altogether. But at least it will be no worse than if you were using real pipes.
However, when using such combined presets with jOrgan in a standard disposition, I think a new kind of problem is produced, at least for the player. To bring such a combined sound into play, you will need to use a stop switch of some sort (or a combination piston), and this could raise some confusing naming issues. The ideal way around this would be for Sven to increase the capability of the MPL so that a logical “IF...THEN” function is provided. Thus if two stops “A” and “B” which are normally available separately are desired to be played together, then the MPL switches on the combined stop “A+B”, and switches off the two separate stops.