Is there a musical term for when a note gradually gets lower in volume in order to point to what will follow?
I don’t kow much about music, so be gentle in your answer. Also, if it exists, I’m looking for the formal name of this “technique”.
Thanks.
decrescendo? It’s been ALONG time since piano lessons, and I only remember seeing a decrescendo used to show that bunch of notes are going to get quieter as you play them, but with the proper note (a whole note maybe) I don’t see why you couldn’t apply it to just one note.
Nothing springs to mind - it sounds like you’re describing something from stage music (for a note held awaiting a cue, for example). Is this what you mean?
(BTW, it’s perfectly possible to have ordinary diminuendos on single notes with the majority of instruments. And you will occassionally find such instructions, as well as crescendos, on music for keyboard & percussive instruments. This probably isn’t the place to get into these slightly philosophical entities 
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I’m not sure what you mean by " in order to point to what will follow" but a fade on overall volume of all parts is a decrescendo, as Joey P. said.
Bo
Do you mean gliding the “tone” down to another note (like sliding your finger on a fret board of a guitar between two notes?)
A note that gradually gets lower in volume is part of a decrescendo, as others have said. I can’t see how a note changing in volume hints anything about the next note, though.
A note that changes in pitch while it is being played would typically be called a glissando. I somehow think this might be what you’re after.
crescendo
A decrescendo can be represented simply by “decresc.” or an elongated “>” like this: http://www.m-w.com/mw/art/decresce.gif
Well, there’s something called “sforzando,” which I’ve always learned is when you have a sudden, quick decrescendo followed by a loud note, sort of to punctuate the phrase or something. It isn’t very gradual though.
If it isn’t decrescendo or diminuendo, are you perhaps thinking of a leading tone? This would be a tone that suggests what comes after. There is also the appogiatura, a grace note. That could be a soft note before the primary note. The grace note could suggest the next note in the piece.
When teaching my students, I often tell them that one way to make a crescendo seem louder or more dramatic is to start softer. Could this be the technique you’re thinking of? In what context are we discussing this?
Thanks all. I’m really getting an education here. What I am looking for is, I would say, laregely emotional and expectant: music trails off softly, but you know that it’s about to get very loud and full immediately.
Ah-hah. Kind of like some of those hard rock 'n roll songs that have that ballad-like intro before ripping into the real song. *Stairway to Heaven *would be an extended version of that, Ike and Tina Turner’s Proud Mary would be more typical. Is this what you’re talking about?
Yes. Good Examples. I know I’ve heard it often in classical music, too. Although I don’t know the names of the pieces (not important). So based on that, which of the suggestions offered would you say is most accurate?
“Introduction”. “Fade-out”, perhaps.
There is no special term for a note fading out in volume and leading to a new section, other than “diminuendo” or “decrescendo”.
I am not aware of a sforzando being used to indicate any preceding diminuendo. In practice a diminuendo may be inferred by the performer, but I don’t think the sforzando technically encompasses it.