I am afraid Black key is right: There is no standard list for the recently (as late as 1955) discovered Chopin’s waltzes.
Eight waltzes were published during Chopin's lifetime (Opp. 18-64). Posthumously, five more were published by Julian Fontana (Opp. 69-70). After this, manuscripts have been found and published without opus numbers and seven have been published so far. With The Alfred edition numbers it's waltzes a little differently than the standard order most are used to. To be honest, there really is no standard order for the posthumous waltzes, but this is the order I believe is most common:
|Post. waltz key| |"Standard" order| |Alfred order|
Waltz in e-.............14..........................16
Waltz in E..............15..........................15
Waltz in Ab............16..........................14
Waltz in Eb............17..........................18
Waltz in Eb(Sost.)....18..........................19
Waltz in a-.............19..........................17
Waltz in f#-............20..........................N/A*
(*=The seventh published waltz is in f#- and is not in this edition. A recording and sheetmusic are available at the Piano Society).
This is correct.
Most editions (well until the1980s) published only 14 waltzes. The Henle edition now publishes 19 waltzes and the Paderewski edition 17 waltzes, arguably the two most authoritative editions.
I am using is the ordering in the Henle edition – which incidentally is the same ordering used by Vladimir Ashkenazy in his recording of the complete Chopin works for solo piano for Decca. This is not to say that either Henle or Ashkenazy have the last word on ordering, but since I often refer to this CD, it makes sense to use the same ordering. In any case this is really a non-problem since as long as one specifies the key and opus number (when available) one knows which waltz one is talking about, and there should be no problem. I am not familiar with the Alfred edition.
But if you would like to be further confused, contemplate this:
1. Henle gives two different versions for four of the waltzes published posthumously: (op. 69 no. 1 and 2 and Op. 70 no. 1 and 2): one version is the one published by Fontana after Chopin’s death, and the other version is the original Chopin autograph. So which version are you going to play?
2. Paderewski, likewise gives two versions of op, 69 no 1 and 2 and op. 70 no. 2, but not of op. 70 no1.
3. There are in fact several versions of op. 69 no. 1 around. [Have a look at: Herbert Weinstock “Chopin, the Man and His Music” – (Knopf) – pp. 296 – 299 for a comparison of the several versions if this interests you]. If you would like to hear the autograph versions (as opposed to the usual Fontana version) of Op. 69 no. 1 and Op. 70 no. 2, see if you can get Peter Katin’s recording of the waltzes for Decca.
4. Henle publishes 19 waltzes in all (following the order I have followed). Number 19 (Eb major) may not be by Chopin. The debate is still raging.
5. Paderewski publishes 17 waltzes in all [it does not include no. 17 in Am and no. 18 in Eb]. Its ordering is slightly differnt again from Henle [no. 14 (Ab) on Henle is no. 16 (Ab) on the Paderewski, and no. 16 (Em) on Henle is No. 14 (Em) on Paderewski]
Waltz no. 20 in F#m does not appear in any “serious” edition of Chopin since it has been accepted by most researchers that is not by Chopin at all.
Personally I think this all Editorial marketing. “Buy my edition! It includes a recently discovered waltz by Chopin, and besides you can have the original autograph edition!” “Get my CD! It has a hitherto undiscovered new rendering of such and such waltz!” You get the idea.
Now to answer your questions:
1. Which Eb is 18 and which is 19?
Both. Both waltzes (18 and 19) are written in Eb major. No. 18 is the one nicknamed “sostenuto”.
2. Is your numbering according to Alfred's or the standard order? The keys indicate Alfred's but the no. 18 and 19 mixup indicates standard order.
As Black key said, there is no standard order. I am following Henle’s edition ordering (and Ashkenazy’s recording for Decca).
3. What's the difficulty of no. 20 in F#?
Around grade 4/5. This is a most beautiful piece. Don’t let doubts about its authenticity stop you from playing it. So what, if it is not by Chopin? It is still very nice (and it sounds far more difficult than it actually is).
Good luck!
Best wishes,
Bernhard.