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.
Now, just a moment... Hymns, Choir, Implicit Ties...

Could you be talking about like Gregorian Chant kind of stuff? AFIK, Gregorian Chant is distinguished in notation by having only four lines, with or without a clef, which may be any letter a-h ("No B♭, that's a Bad B♭!").

Older than that is notation based on 'neumes' which I never really understood. But neume comes from 'pneuma', greek for spirit or breath; so with both of these, the notes comprising one word of the text are to be sung as if tied together.

For software, I'd search for something with a Chant mode, or a plugin or something. This has got to be already-explored territory. 2¢