I have a score in 4/4 time with the following measure:
My music program (MuseScore) plays this with the two 16th F notes "in between" beats 2 and 3, with the second F/C chord playing at beat 3 and the F/A dotted eight playing at beat 4.
Question: what in the score indicates that you should play those 16th F notes "in between" the beats as opposed to playing the full quarter note at the second beat and then the 16th notes? In other words, to my eyes, these notes shouldn't all fit... the F note at beat 2 should be an eighth note not a quarter note. What am I not understanding to read this correctly?
You're right to be confused, this is notated incorrectly. My best guess is that there's a second voice, so really there should be a quarter and eighth rest before those notes (below the existing quarter notes) and a half rest afterward, and whoever wrote this went through the extra effort to disable them from the display. They could also be grace notes, but the stem directions seem to indicate the two-voice thing.
Yes just play two notes before the 3rd beat there will be only one way to do that its impossible to do that in 4/4 time incorrectly without knowing it if you have any feel for melodies at all. If it supposed to be there and you don't play it or its not smooth when you play it you will mess up the entire melodie. Its those little lead in or grace notes that gives it life otherwise its just stagnant.. Play it like it looks and see what happens..