The Rank.Samples_RankBasePitch64ftHarmNumIfAssumedTunedToConcertPitch attribute is used to tell Hauptwerk how to determine the pitch of the sample files. This is the relevant excerpt from the CODM user guide for it:
Hauptwerk must know the exact pitch of each sample so that the required amount of re-pitching can be calculated to play the organ with any user-selected temperament. The sample set creator can either have detected the exact pitch of the samples and saved them into the sample files, or have re-tuned the samples perfectly to concert pitch (A=440 Hz) and equal temperament.
In the former case, this parameter should be set to zero (in which case Hauptwerk will read the sample pitches from the samples themselves). In the latter case (samples tuned to A-440/equal) then this value gives the pitch of the samples by specifying the harmonic number that they represent, relative to the fundamental of a 64' stop. For example, if the samples were recorded from a 4' rank, then the pitch of the samples is considered to be 4', which corresponds to the sixteenth harmonic of a 64' pipe, and thus 16 should be specified for this setting
Provided that the sample set producer has designed the sample set to be compatible with the CODM (which we highly recommend in the sample set creator's guide), you should be able to see the correct value to use by looking in the CustomOrganRank in the package definition file that contains the samples, and if that value is used in your CODM ODF then the ranks should automatically be in tune.
If that isn't the case then I think that one of the sample sets must:
- Have incorrect pitch values stored in its samples, and/or:
- Not have had its samples tuned perfectly to A-440/equal.
If both of those are true then the sample set doesn't doesn't adhere to the guidelines in our sample set creator's guide and isn't properly compatible with the CODM, since there's no way that Hauptwerk can know the pitch of the samples, and thus no way it can work out reliably how much re-pitching would be required in order for the pipes to sound correctly at any temperament and base pitch chosen by the user. No amount of fiddling with the output pitch settings for the rank is likely to compensate for that properly.
Looking in the package definition file for the Notre Dame de Metz, the CustomOrganRank entry says that Rank.Samples_RankBasePitch64ftHarmNumIfAssumedTunedToConcertPitch should be set to 0, indicating that the correct pitch will have been stored in the samples, which I'm sure is the case anyway for all Milan Digital Audio sample sets.
I don't seem to have a copy of the v2 Caen, but from an older version I have, the package definition file doesn't have any entries in its CustomOrganRank table, so I'd suggest contacting its maker (Jiri -- Sonus Paradisi) for whether the sample set has the correct pitches stored in its samples, or whether its samples are tuned to A-440/equal, or neither.