Question: Is there any "rule of thumb" regarding playing notes in both clefs, at the same time? In other words, do the stems need to line up or do the notes need to be directly over each other? In classical music, this is pretty straightforward. However, in contemporary music, I run across situations in which neither the stems nor the notes line up directly, and I wonder if these notes should be played at the same time?Lee (La Quinta, California, USA)
If the music was typeset using computer software, as is the case with every publisher nowadays (to my knowledge), it's almost certainly the case that the notes will align with each beat or subdivision thereof, since the note spacing is mathematically calculated. Interestingly, aesthetically pleasing note spacing is not mathematically precise; it is thus as much an art as it is a science. The designers of the open source music notation software Lilypond have taken these mathematical imperfections into account in their brilliant music engraving algorithms.
Older editions will have been typeset by hand and thus may be imperfect in terms of note alignment among the staves. Two things are important to note in this connection: First, hand engraving, done with the aid of the eye, like an artist, is very much valued, even in today's digital age.
More importantly, we need to count the rhythm in each staff and each voice no matter how perfectly the notes may be aligned. Fortunately, this isn't as hard as it might seem, even to early intermediate-level students. The reason is that the rhythm is constant, as determined by the time signature. As long as you continue to count the beats, keeping in mind the important distinction between simple meter and compound meter, you'll be able to tell immediately which notes are meant to be played together.
In summary, you should always rely on counting each voice to determine which notes should be played together. The printed sheet music should be properly aligned, but never rely on this alone! Looks can indeed deceive.