Sorry I do not know of any software that comes up with lyrics (a story line), melody (treble clef) and harmony chords (bass clef) all at the same time for you. And we have yet to speak about rhythm..... That kinda develops somewhere in the matching of the melody notes to the lyric flow. So I offer the following:
My songs are sung, so..... if there is no story to be told, there is no reason for the song. Once you have something worth being told put it into verse form; if it still sounds like something that needs telling, get busy making it a song.
The following is a dirt simple generic "pattern" that you could use. Four line verse. Three verses, one chorus for the first draft. Yes there will be several more drafts. I write in the key of C. Why. Simpler. And the ole I-IV-V will get you started. My music, Country and Praise, is mostly in a major key. You may want to write in a minor key. If this is your first draft major probably will be easier. Some say major = happy and minor = sad. That is over simplifying the issue. Use which ever one you are the most comfortable in.
You already have your lyrics into three verses and one chorus; time to decide on a key. Let's use C major for this example. And here we will place the chords for this song at specific places to obtain movement for the lyrics. A dirt simple example could be - start your first four line verse with a C chord and near the end of the first line of the verse bring in the F chord. Continue with the F chord into the second line and near the end of the second line bring in the G7 chord and then end the second line back with the tonic C chord. That will give you a V-I cadence in the first two lines. Do it again in the last two lines of the verse. Those two V-I cadences move the song along within the verse. We'll get into melody and harmony in a moment.
Normally the first two lines of a verse bring up a thought and the second two lines bring this thought to an end. So the second verse can bring up a new thought... The chorus is what you want them to be singing tomorrow. Don't worry with bridges, pre-chorus, etc. right now. This is a first draft.
Do the same for all three verses and the chorus. Now strum or chord on your keyboard the progression while reciting the lyric words. You'll want to move the chord changes one way or another to match the lyric flow.
Again using a simple solution -- have your treble clef and bass clef harmonizing with each other by drawing your melody notes from the chord tones or the pentatonic scale of the active chord.
While the C is active the melody should share some of the same notes found within the C chord. When the music moves to the F chord the melody now should use some of the same notes found in the F chord. Why? If the melody line and the chord line share notes harmony happens, and that is a good thing.
How many melody notes need to be shared with the chord line? One per measure, that is why pounding roots works. Two per measure is better, however three are probably not needed as one got harmony.
Now back to melody - stay in key and help yourself to melodic phrases built around the chord's tones. Keep in mind that this song is in the key of C and melody notes from the C major scale could be used for the entire melody. You will, however, have to see that the chords we placed in the song now have shared notes with the melody. This can normally be accomplished with out harming the movement we have established by the use of extensions, like a sus2 or sus4, a 9th or 11th, etc. Point - the active melody line and chord line must share some like notes. So add a harmonizing note to the movement chord so it two will move and harmonize.
Notice I started with lyrics, then chords, then melody and then a bass line. You could start with the melody first, however, when you finish melody harmony and rhythm need to go through this harmonization process, i.e. they all fit together.
That will get you a lead sheet. Lyrics, treble clef and chords used shown above the lyric words.
Let the bassists work out his/her own bass lines or go ahead and write the bass line in the bass clef.
Ok that takes care of melody and harmony. Rhythm is dectated by the song.
Take that big pencil and start with a story. A good eraser that does not leave a smudge and a keyboard with some blank staff paper for the melody are some of the tools you will need. A little theory on how to harmonize a melody line will come in handy.
Melody notes, if you decide to not use notes of the chord and go with the C major scale, recite the lyrics until a melodic phrase comes to mind. Three close notes then a leap of at least a 3rd seems to work out and follows the 4/4 time signature. Each lyric syllable normally takes a melody note. For example; hap-py gets two notes as would birth-day. The words "to and you" get one note each. Keyboard works great for fleshing out a melody.
Now you understand why songwriters want to protect their work.
Good luck.
