Sayuri : "i was wondering if you were going to add harmonies or chords with your songs..."
The semi-question statement you left is a bit confusing. I'll answer by parts.
Harmonies and chords are part of all songs, not just bits that can be excluded by intent. All my songs have at least 2 if not 3 chords (to use Mabi terms). Just because it's in the MML block format does not mean it's not got all 3 lines you are used to seeing in a scroll as you compose it. If you find this a bit confusing, see the FAQ page.
If your question was intended to be "Are you going to eventually add vocal lines to your songs?", then the answer is yes, for some. It is not going to be soon and will take a ton of work on the site to change the layout just enough to add that extra line where it is needed.