I thought that the auxiliary note of a lower mordent (or other ornaments) was simply the note before in the scale unless the mordent had an accidental on top of it. However, I ran into this discussion providing a much more complex rule explaining essentially that the auxiliary note should be a half-tone down unless the note played immediately before or after the mordent was a full tone below or when the mordent is applied to a 3rd or 7th. Given that I never heard this before and that the full discussion leaves a lot of confusion as to how the accidental should be interpreted in that case, I am having doubts about that entire explanation.

Can someone explain simply what are the rules for playing the auxiliary note of lower (and upper) mordents, with and without accidentals? Examples welcomed.

Thank you

  • AFAIK, you may choose yourself. It's either that, or I have been doing it right instinctively since I arrived at repertoire with mordents, as my teacher never objected.
    – 11684
    Nov 3, 2013 at 21:40
  • I have done it instinctively myself as well for many years and my intuition is clashing with what I recently read in the pointer I provided. Hence my question. I am very much interested in knowing what the actual rule(s) is(are).
    – Lolo
    Nov 4, 2013 at 0:50

1 Answer 1


I got an answer to this question after talking to a few musicians.

The auxiliary note is determined by the melodic context.

For example, in D major, an auxiliary F and D should be raised. Now, the trick is that there may very well be modulations so, for example, a piece starting in D major could turn into B minor, in which case the 7th (A) will likely be raised as it is typically in the minor classical scale. I say "likely" because the song could be in minor but use a natural minor scale instead of the more common harmonic scale. If that were the case, the A would not be raised.

In short, to a first approximation, one can just look at the alterations on the staff to know what auxiliary note to play and will be right most of the time, but to be sure, one should listen to play what is correct accordingly to the current melodic context.

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