Question: Is there such a thing as an implied tie? Like some kind of symbol or notation that would specify to hold a note through the duration of all the notes on a pitch as if they were tied together. 

**Edit:** I am asking because I am wondering if there is a way to specify that instruments hold one tone (like a choir that is humming) instead of playing each note separately. The reason I am wondering is because I am using a notation program to write out some music, and then you can listen to it, and I want to hear it like a choir humming. I know about ties, but I just thought I'd check if there is such a thing in music.

**Edit:** By implied, I mean it isn't written in the music. In other words it is specified at the beginning of the part or something like that. 

**Edit:** I am using Noteworthy Composer.

Answer: 
As I understand your question, no there is not. A tie is always written out with a curved line connecting two or more notes of the same pitch. 

The only thing that I can think of that comes close is a dotted note. However, a dotted note is viewed as one note, not multiple notes tied together.
In guitar music you occasionally find the remark "Let Ring." This means tones are held as long as possible, until that finger is required elsewhere. A somewhat similar effect is produced by holding the sostenuto pedal on a piano. 

[Perhaps my terminology implies more expertise than I actually possess. I learned on an antique player-piano with the player mechanism discarded. It had a pedal that moved all the hammers closer to the strings thus curbing the range of accelleration, the 'piano' pedal. And it had a pedal to raise all the dampers so every tone rang until it had diminished below the threshold of perception. It is this pedal that I mean by 'sostenuto'. To use it musically, you have to *clear the memory* while sounding a new chord, so as to have no gap in the sound. There are some fancy "modern" pianos that can sustain only the notes currently being played, allowing staccatto on the other keys. The player-pianos of yore did not have this ability.]

While the staff notation would be no different than *not doing this*, it does seem to require explicit instructions (e.g., "Hold pedal until a chord can hide the pedal change."). Instructing software to do this would be somewhat different than instructing musicians.