Hello Christoph,
There are two separate attributes in the CODM's Rank table:
Samples_RankBasePitch64ftHarmNumIfAssumedTunedToConcertPitch
Pitch_RankBaseOutputPitch64ftHarmonicNum
There's no definitively correct choice of value for compound stop samples. However, sample set producers would usually specify the 'base pitch' of the lowest of the compound pipes if the stop's ranks are unbroken across the compass, although in the case of mixtures (or other stops with broken compasses) often a single value is specified for the whole rank to approximate/represent the overall effect of the stop, or for a rank that's prominent throughout the compass -- probably 2' most commonly.
The important thing is that the values you specify match the values that the sample set producer used when they stored the pitch within the sample files when detecting their pitches. The sample set creator's guide highly recommends that sample set producers specify the necessary values for each rank with the following two attributes in the sample rank's installation package definition file, in order to make the rank fully compatible with the CODM (unless the sample set's licence specifically doesn't allow use of the sample set in the CODM):
CustomOrganRank.TunedToConcertPitchAndEqualTemp
CustomOrganRank.RankBasePitch64ftHarmNumIfTunedToConcertPitch
If the sample set producer hasn't included the rank details there (but does allow use of the sample with the CODM), then you'd probably need to:
- Contact them to request the relevant values, or:
- Experiment with different values to see which one works. If a mixture, then see whether assuming its pitch to be 2, or 4' or 1' gives the expected pitch.