I came across a bar that sounds like this while transcribing a piece for keyboard. Is there a correct/better way to write this?
A broken chord like this is notated with double stems for each note. One set of stems corresponds to the eighth-note onsets of each note. The second set of stems corresponds to the duration of each note and shows the tie to the final, full chord.
It is acceptable to use shared note heads in this kind of situation. For example, the first note could have a half-note head, but an eighth-note stem.
Here is a similar example from the left hand, final two measures of Brahms's "Intermezzo" Op. 119, No. 2.
A second example, from Chopin, shows the importance of the ties versus a simple pedal indication.1
This first image is the first four measures of Chopin's Prelude in C major, Op. 28, No. 1, from the Paderewski edition (i.e., this is Paderewski's interpretation of how this should be played). Note the one-pedal-per-measure scheme, which is marked "Ped. simile" ("keep pedaling in the same way") in the fourth measure.
However, this notation clearly does not mean to hold all notes of the chords. The sound would be extremely muddy. Consider this notation is light of the final three measures (mm. 32–34), shown below. Measure 32 is played as shown in mm. 1–4, but measures 33 and 34 are explicitly tied to illustrate the intention of a slowly arpeggiated block chord. (Also, the absence of double note heads is another alternative notation that is sometimes used.)
Just based off of the span of these pitches, most players can't play all of these pitches with one hand (assuming either a B♭–D or B–D♯ span).
As such, I would argue that pedaling is the best bet. Just write the pitches as normal eighth notes, but indicate to the player to hold down the pedal, thereby sustaining the pitches until the pedal sign changes:
It's true that pedaling could muddy up the melody notes in the right hand (depending on how active they are), but an accomplished pianist should be able to use pedal without sacrificing melodic clarity.
If the right hand is too much for the pedal, you could also clear up the notation by using simple eighth notes (as in the above example) but with a text indicator to the performer: "sustain all left-hand pitches for the duration of the measure."
PS: How funny that When piano pedalling seems to conflict with the original score was asked almost simultaneously with this one, since it connects with my answer exactly.
That's the way I've seen it. Obviously a wavy line won't do the job, a player would play the notes too quickly in succession.
The other way would be to write the lowest note as full value, and write as SATB, using rests before each of the other notes, which would then have their own appropriate values, losing a quaver each time in your example. But that's even messier.
Or - write out the first 3 quavers consecutively, each tied across to those same notes to, say, a minim chord to fill the bar. It's not technically correct, but tidies it all up, and the expected result is more than apparent.