[MEI-L] encoding orchestra cast with alternative instruments

[Benjamin W. Bohl]

Dear MEI-L:isteners,

can anyone help me how to encode a cast list for an orchestra that gives alternating instruments for the players and potential replacements if certain instruments not being available?

E.g.:
In the cast list:
“3 Oboes – 1. And 2. Also oboe d’amore, 3. Also cor anglais”

Amongst other at the end of the cast list:
“If necessary, the oboe d’amore can be replaced by an oboe, […]”

Simple case ignoring additions:

<perfMedium>
    <perfResList>
        <perfRes codedval="wb" count=“3" solo="false"></perfRes>
    </perfResList>
</perfMedium>

Alternatively trying to capture all instrument info:

<perfMedium>
    <perfResList>
        <perfRes codedval="wb" count="3" solo="false">
            <perfRes codedval="wb" count=“3" solo="false">Oboe</perfRes>
            <perfRes codedval="wz" count="2" solo="false" >Oboe d'amore</perfRes>
            <perfRes codedval="wz" count="1" solo="false">Cor d'anglais</perfRes>
        </perfRes>
    </perfResList>
</perfMedium>

Nevertheless I can’t capture the idea of alternating instruments for the first two oboes resp. The oboes d’amore or the third oboe and the cor d’anglais…

What if I use even a deeper nesting:

<perfMedium>
    <perfResList>
        <perfRes codedval="wb" count="3" solo="false">
            <perfRes count="2" solo="false">
                <perfRes codedval="wb" count="2" solo="false">Oboe</perfRes>
                <perfRes codedval="wz" count="2" solo="false" >Oboe d'amore</perfRes>
            </perfRes>
            <perfRes count="2" solo="false" >
                <perfRes codedval="wb" count="1" solo="false">Oboe</perfRes>
                <perfRes codedval="wz" count="1" solo="false">Cor d'anglais</perfRes>
            </perfRes>
        </perfRes>
    </perfResList>
</perfMedium>

I’m not sure whether this captures the meaning, especially since there is no possibility of stating the exclusive alteration, like e.g. in TEI with @exclude.

Any thoughts would be appreciated!
Many thanks
Benjamin