I always have trouble finding the key of the song, actually when ever I write a song just lyrics and I know how I sing it I mean I know the composition, but I don’t get to know what should be what scale or what key these lyrics are in. I need help to know how to know what scale I wrote these lyrics in so that I can easily extract chords and put the vocals in my DWA to make more music on them.
Firstly, lyrics don't have a key, they are simply words, like a poem.
A melody does not have a key. It may imply a key but this is open to interpretation and opinion based.
Eg consider the first seven notes of 'twinkle twinkle little star"
(starting from a C note)
These notes appear in:
(these lists shorten somewhat if you analyse the entire melody)
As you can see there are many choices and there are literally thousands of ways to harmonize a melody. You use your ears to guide you to the appropriate chords for your melody.
The original composer chose to do it in this way:
Melody notes: C C G G A A G Chords: Cmaj Fmaj Cmaj
Major, very consonant, simple I IV I progression, perfect for a childrens song.
Here are some alternatives:
Melody notes: C C G G A A G Chords: Am Am7 D7 G Melody notes: C C G G A A G Chords: Am Em Dm Cmaj Melody notes: C C G G A A G Chords: F Gm Am Em Melody notes: C C G G A A G Chords: Cm Gm F7 Bbmaj6 Melody notes: C C G G A A G Chords: Dbmaj7 Bbm9 Edim Am7 Fmaj9 D7 G6/9
Play these and hear how they change the character of the melody.
All of my examples are based entirely on chord tones: The melody note occurs within the chord. It's a fool proof way of finding chords that fit your melody. It is (or rather can be) also a road to very boring songs as non chord tones are required for tension & drama.
As you've written your own melodies you probably have some preconceived idea (possibly subconscious) as to how it should be hamonized. Try:
Experiment with chords from the key you have identified. The I IV and V chords can harmonize any diatonic melody so start with them. Work at it until you find the chord progression that you think suits.
And most importantly LEARN SONGS! How can you expect to write great songs if you can't identify what a great song does?! Learn and analyse songs you like to see how the melody and harmony fit together and what it is that makes you like the song.