I'm a beginner, and confused about the fingering on this measure

Harrie Bannink Agreed, although the fingering without the mordant might be different, albeit not in this example.  

Harrie Bannink I would like to offer the suggestion that using the term "song" is not appropriate here -- "piece" would be much  better. Since Tom is a beginner, it's important that we provide him with the correct terminology.

Eder Giaretta but use fifth finger on the mi.

Roy James-Pike The human wrist doesn't rotate. It's a common misconception in piano teaching to refer to "wrist rotation."

In any case, this mordant is most easily played with finger articulation alone. (Forearm rotation will only get in the way here.) I find starting on 5 and playing the ornament 3-2-1 (like Eder and Patricia suggested) to be most natural and suggested this in my own edition.

I also agree with Harrie that it's a good idea for complete beginners to omit any ornaments at first. In this case, starting with 3 on E works best.

Regardless of which finger you play the E with, it should be articulated (separated slightly from the C that follows) for reasons of style.

Hope this helps clear up any confusion.

Albert I was merely responding with my personal suggestion to someone who made a simple request for help about how to play the thumb followed by the index finger playing a note below the thumb and the same finger being played subsequently on the note above the key played by the thumb.  

My description of 'rotating the wrist' referred to what it looks and feels like when doing this, which is the fingering given in the score.  It was to explain how we cross the index finger over the thumb economically, and then back again.  It was not intended to be a precise physiological conceptualisation of the process. 

I have suggested elsewhere to this beginner that they try different fingerings when the given fingering does not work for them.  Therefore, they may try your suggested fingering too, along with all other suggestions.  They can then decide which feels better for them, which, as stated elsewhere, is never set in stone.    

It's interesting that you say that this misconception is common amongst piano teachers, which is probably due to their experiences being the same as mine.

I referred to Penelope Roskell for professional advice on the issue of rotation, which is available on Tonebase, as is Taubman.  Penelope discusses finger independence too.  I suggest again that they check out advice from the TB teachers.  

Roy James-Pike Thanks for your clarification—appreciated. If I may, a mordant isn't an application of rotation (wrist, forearm, or whatever one prefers to call it) in any method I'm aware of. I'd really advise against it here. Rotation would only interfere with articulating the notes quickly and clearly, as mordants require. It's possible (and in fact easier!) to play this ornament with 1-2-1 or 3-2-1 cleanly with finger articulation alone.

If beginners are struggling to play this ornament fast enough and still want to play it, there is a way to "cheat" that Paul Badura-Skoda once showed me. (This is "top secret"—shhh!) :-) Just play and hold the main note (C), then immediately play the lower note B staccato. Release the B as soon as you play it, all while holding the C. It's probably easiest to play 3 on C and 2 on B in this case. It will go by so fast that it will sound like a perfectly clean mordant of three notes when you only played two... no one will be the wiser!

That said, I do think this mordant is something maybe all but complete beginners can do with a bit of practice. If you can tap your fingers 3-2-1 on a table quickly, it's not too much of a jump to play C-B-C with the same fingers. Just keep your wrist free of tension (Penelope has a good exercise for this) and the fingers will be free to do their job.

Albert The student asked for an explanation of how to play the given fingering in the score.  May I suggest you take it up with Tonebase if you think the given fingering is incorrect. 
I saw Mitsuko Uchida play Beethoven’s 4th some weeks ago. I recall her playing double trills in one of the cadenzas. She was rotating magnificently between 1 and 3. 

Roy James-Pike I didn’t suggest the fingering is incorrect—in fact, this same fingering is one that I suggested as a possibility.

I’m also not sure why you seem to feel the need to be defensive. This is a friendly community with professionals and amateurs alike and there’s a lot that can be learned here.

If I may, I’m guessing that rotation may be one of those “if all you have is a hammer, everything looks like a nail” things.  A mordant isn’t an application of forearm rotation in any methodology that I’m aware of. Honestly, trying to rotate here would only make things harder. Whether you use 1-2-1 or 3-2-1, finger articulation is so much easier.

As for the trills in Beethoven’s 4th Concerto, extended trills are completely different from mordants technically. Many players, including some professionals, do use rotation for extended trills (personally I reserve this technique for the octave trills in Brahms’s 1st Concerto). Maybe it’s worth noting that such a technique works on a modern grand piano with a double escapement mechanism if you choose stay in the key; on fortepianos of Beethoven’s day players would need to use pure finger articulation and release the key completely.

Hope this helps and that you’ll give these small suggestions a try. Wishing you lots of musical enjoyment in any case.

Albert It’s really not very polite to tell people what they are thinking and feeling, but for clarity, I’m not feeling defensive, or thinking that I need to feel defensive.

I am an empiricist. For more clarity, I shall say again that I was responding to the particular question, which was how to play this particular fingering.  I have agreed in a number of places that alternative fingerings should be considered. My view is that this involves rotation, even if it is minimal, in order to cross over from the thumb with the index finger and back again.

In fact, my personal preference for this phrase, taken in isolation, would be to start on the E on my pinky and use your suggested 321 on C B C, as this sets up being able to travel up the keyboard in C major with the standard fingering.

Have a nice day. Jazz is calling.  I always enjoy my music and always have. It’s the place where I go to avoid other people.

Roy James-Pike In writing, like in music, sometimes how we think we sound isn't how we really sound. That holds for me as much as anybody else. Let's strive for a friendly tone on tonebase.

As for using rotation for the mordant here, if a student were doing even a little bit in this case, it would be a clear sign that something is wrong. Often we use other parts of our playing mechanism, usually subconsciously, to compensate for deficiencies that could generally be quite easily corrected with guidance and care. In this case we would need to work on freeing up any unnecessary tension (the wrist is the usual culprit), then on independence of the fingers and wrist, then on articulation, control, and so on.

That said, if a student were, say, an amateur with arthritis, then we'd have to work within their limitations. Barring that, I see no reason anyone with normal hands should resort to a crutch like any rotation here. Rotation only makes it harder and interferes with control of the keys.

But for complete beginners, I'd recommend omitting the ornament altogether here.

Hope this helps clarify everything. Enjoy your jazz-filled afternoon. That's a talent I wish I had.

Albert It would be useful to be able to see (and hear) ourselves in the way that others see/hear us. 

For further clarity, I do not have any known deficiences, at least not yet, nor am I disabled, either with arthritits, or in need of a crutch.

I am applying concepts in my playing that I have learned on Tonebase, and elsewhere.  I have referred to Penelope Roskell's teaching and Taubman in previous posts.  I am applying those techniques so that pain, discomfort, and injury, through inflexibiity is avoided.

Their concepts appeal to me more than your suggestions, unless I have misunderstood the latter.

I do not see that there is any benefit for either of us in continuing to pursue this exchange.  We have different views.  It's as simple as that.

Roy James-Pike Can we kindly keep things amiable? This is just piano playing, not politics. We're all on the same team here, after all.

Someone please correct me if I'm wrong, but I suspect there may be a misinterpretation at work here. With nothing but full admiration for everything amateurs accomplish at the piano, I'm guessing you may be applying a technique in a place where it might not be intended.

The original question was how to play a mordant C-B-C with fingering 1-2-1. As far as I'm aware, all professionals, myself included, play this with finger articulation, as this is one of the most basic movements in piano playing. (Surely there's the odd exception that only proves the rule out there somewhere.) The tonebase teachers mentioned may use forearm rotation in other contexts, but it seems to me to be a stretch to assume that they would also recommend using it for a mordant. Mordants are by definition played very quickly, and rotating the forearm is slower than simply articulating two fingers in succession (the third is held and thus not immediately articulated).

My understanding is that the aim of these techniques is to play naturally, efficiently, and with simplicity and ease (whether a given technique achieves its aim is another matter), so it wouldn't make sense to over-complicate so simple a movement by introducing an awkward one (in the case of a mordant) that slows us down without offering any advantages. (Since it's so difficult to describe something as complex as piano playing, too often even professionals end up describing things in a way that they don't actually do themselves—but that's a topic for another day.)

Techniques and methodologies do differ. They're not all created equal, and not all roads lead to Rome, but I think there's a consensus in this particular case, in action if not necessarily always in words.

I think this discussion highlights the ongoing need for expert, guided instruction. Grateful for a community that continues to see the value of teaching in a world gradually replacing human skill with apps.

Hope this clears everything up. Wishing you a very musical Sunday and looking forward to friendly discussion in the future.