Wed Oct 14, 2020 10:25 pm
Thanks for your feedback! Other have also commented on my mixtures, I’m glad you liked them. I’m planning on making a blog post where I go through mixture design in more detail, but I can briefly explain what I did for this organ.
Generally I use flute or principal ranks for my mixtures, and in this case I believe I used St. Anne’s Fifteenth 2 for the Great German mixture ranks. Depending on the harmonics, I voice them by decreasing the harmonic amplitude (usually -3 at top and bottom, and -2 for the wind model top and bottom). For a complex mixture like this, I create a custom rank for each run of pipes. For instance, for all the 2’ pipes, I will have one CODM rank. If there is a split in the pipes, I will make two ranks (say, there is a 2' from midi note 36 to 47, then again from 60 to the top). Then I do the 1’, 1/2’, 1/4’ etc., then go lower - 4’, 8’, etc. Then I do the same for the 1 1/3' ranks. For each rank, I adjust which sample is used so it corresponds to the actual pipe size (for a 1' rank, +12, for a 1 1/3' rank, +8, for instance), and I use the appropriate harmonic number (so they are all tuned harmonically). I then listen to the mixture and if I think it is too bright, I will back off on the volume of each rank. However, I usually only start decreasing the volume for ranks over 1 1/3', and the higher they go, the more I decrease the volume. For instance, for this mixture, The 2' was volume 0, the 1' -1, the 1/2' -2, and the 1/4' -3. Therefore, for a 3 rank mixture, I will often need 5-7 ranks, depending on the mixture design.
When I was developing this mixture design, I found that it created a more interesting variation as I went up the scale if I varied which ranks were omitted. For instance, in the example you mention, I omit the 2' in the second octave, but reintroduce it in the third octave. There is no 1' or 2/3' in the first octave, but they both appear in the second octave.
I’m also working on a version of this organ where I improve the voicing of the tremulant and a few other tweaks. I will post here when it is done.