>> I was engraving a piece of chant in modern notation recently, and
>> discovered that none of the custodes will draw a ledger for middle
>> C (C4) or A5, notes beyond the 5-line staff. These notes do occur
>> in chant and polyphony. [...]
>
> Perhaps this: [...]
>
> The above hack does nothing more than add a fake NoteHead that
> overlaps the Custos grob so that the LedgerLineSpanner does its
> magic.
Thanks for the workaround code! Anyway, I consider this a bug; it
should be added to the tracker.
Werner