I'm composing a piano piece and I'm trying to make the accompaniment.
I made this arpeggio and I had this thought that
the Bb/F might not be a Bb/F.
Because it's starting from the Bb.
But what if I hold down the pedal for the entire measure.
would that make a Bb/F ?
If you held the pedal for the whole bar it would make a mess. There's an F major for the first two beats, then a Bbmaj7 for the other two. All far too muddy. Yes, it may constitute Bbmaj7/F, but it's not good music. With a sostenuto pedal, it's quite feasible, and would work and sound good. But then the first F note would not be a quaver - it'd be a semibreve.
Maybe there's too much theoretical thinking going on. Please remember, theory came about as a way to explain what happened. It's not something to be adhered to, or even as a check-up on what's been played. That second chord is simply Bbmaj7, if you need a label.
And - we don't know what else is going on in r.h., so we're pretty well in the dark.
If you hold down the sustain pedal for the whole measure you'll get a mess!
If you find a way to sustain the low F you can call it F, Bb/F. Or, more accurately, F, Bbmaj7/F.
You could 'half-pedal' it. But that works best when the note to be sustained is clearly in a lower register than the ones to be damped. Or you just MIGHT have a big enough hand to play it literally!
Even if you don't sustain the F, the harmonic intention can still be F, Bbmaj7/F. Particularly if the first note of the NEXT bar is also low F.
the Bb/F might not be a Bb/F. Because it's starting from the Bb.
Yes, it's a Bb/F
But what if I hold down the pedal for the entire measure.
would that make a Bb/F ?
That's a bad Idea. Why hold the pedal for the entire measure? It will sound pretty wrong for this style.
You need to change the pedal at beat 3 for the new chord.
The arpeggio you labeled B♭/F, if it's distinct from the first arpeggio, does not have F at the bottom, so it's not B♭/F. The second half of the measure is actually forming a B♭maj7 chord. If you're sustaining over the whole measure, you would end up with an F6add11 at the end. It's not that messy. (Or maybe you could call it B♭maj9/F. There is no context, so it's hard to say.) In any case, the second chord symbol isn't representative of what's going on.
Given what you wrote it seems your are arpeggiating these chords...
...where D is the bass of the second chord.
It seems Bb/D would be the label to use.
But the ambiguity of whether the F bass of the first chord is somehow held or implied under the second depends a lot on what happens in the third chord.
To illustrate the point I made up a C chord for the third chord. With that change to C I think a Bb/D label is sensible.
You could do something else that would make different labels more appropriate.
