Are there different rules for double notes fingering (piano) for legato vs. staccato?

Question

If the double notes are legato, is it a rule not to involve the same finger when playing two double notes in a row? If so, is staccato subject to such rule?

In particular, in the following Bar 45 of Beethoven Op.49 No.2, Movement 1, the fingering in colors is what I'm used to, but I wonder if I should avoid using finger 2 again on the 4th (last) double notes? Or is it acceptable because it's staccato, not legato?

Thanks for all your help. I'm learning by myself.

Answer 1

TL;DR

For double notes, including double thirds, some situations allow for use of the same finger on consecutive notes, and some situations specifically demand it.

This is true for both staccato and legato articulations, though it's more common in legato, to preserve the smoothness; whereas, staccato allows for more flexibility.

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A common situation — repeated thumb

One frequently encounters runs of four double-notes, similar to those in the Question. When ascending in the right hand or descending in the left hand, it's very common to use the thumb twice consecutively. This is especially the case for legato, where using the thumb twice in one voice allows for a true legato in the other.

X: 1
T: RH Double Thirds
T: Repeated thumb
K: D
M: 4/4
L: 1/4
("2""1"[DF] "3""1"[EG] "4""2"[FA] "5""3"[GB])

X: 1
T: LH Double Thirds
T: Repeated thumb
K: D clef=bass middle=D
M: 4/4
L: 1/4
("1""_2"[GB] "1""_3"[FA] "2""_4"[EG] "3""_5"[DF])

The OP situation — repeated finger 2

In the Question, the above repeated thumb option would be viable, but there are two good justifications for the given fingering:

1. Legato is not a necessity, and
2. The C# is easier to access with finger 2, which is longer than finger 1.

The finger "drag"

Sometimes within a pair of consecutive double-notes the upper or lower note will move from a black key to a white key. In this case, it can be useful to "drag" one finger along.

As an example, consider Chopin's fingering for his Etude in double thirds, Op. 25, No. 6. In measure 5 (below), note that finger 2 is used to move from D# to Dx and then later from A# to Ax.

(SOURCE: Henle Urtext)

This technique can be applied to any finger, particularly when that finger can move from a black key to an adjacent white key.

Repeated fingers by necessity or design

Rapid octaves

In Chopin's Polonaise in Ab, Op. 53, there is a large section (mm. 58–120) of mainly very fast left-hand octaves.

(SOURCE: IMSLP, Mikuli edition)

Depending on one's hand span, every pair must be played with fingers 1 and 5.

Octave glissando

In Beethoven's Sonata in C, Op. 53 ("Waldstein"), the third movement contains several glissandos of octave double-notes. This cannot be played as intended without using the same pair of fingers throughout. The below image shows measures 467–72.

(SOURCE: IMSLP, Breitkopf und Härtel complete works)