Decide on a key. It is important to bear in mind the vocalists range when deciding on a key based on the intended nature of the melodic voicing. When working with vocals it is good practice to first establish an appropriate key bearing in mind the initially perceived song idea. Alternatively once a chord sequence or progression has been decided upon, it is not uncommon to transpose the song to another key when working with vocalist to adapt something already written to a vocalists range. Sometimes it is hard to find the right melody for a song, transposing a sequence can often be enough to allow the vocalist to find and hit the notes that work best for the sequence aiding in versatility.
Major and minor, typically associated with happy and sad. When deciding on the nature of the chords used they can reflect the nature of the mood and feeling of the song you are creating and further enhance the impact of the song on its listeners. It is possibly important to bear in mind the nature of the song you are trying to create before deciding on weather a song will have a major or minor feel. Though it is not uncommon to create a sequence that simply sounds nice first and adding the rest later based on what the songwriter feels the sequence demands or what naturally comes out. It is not necessary to stick to key entirely. Try different things out to see what appeals to you. This can create interesting shifts in mood and/or the progression of the song.
how many chords in a sequence can help to define the way in which the song progresses, particularly with the vocal application. When using three chords for example, i can allow the vocalist to experiment a bit more vocally as the sequence of the particular section is very predictable. When suddenly using 8 chords in one sequence it suddenly means the vocalist has to potentially do less due to the demand of the sequence. This is why it is important when deciding on how many/what chords to use in the song. If the chords are the first thing to be written, it is good to go with what feels right with the composer, but again it is good to experiment in order to potentially find something more interesting than a typical sequence.
RHYTHM & HARMONIC RHYTHM:
Combined with the sequence itself is the harmonic rhythm of a song. This is defined by the rate or speed at which the chords change and on what beat in the bar. Syncopation comes into play again potentially. chords can be changed on the beat, before the beat, after the beat and combined with the time signature can make a song significantly more interesting to the listener. It also defined the overall feel of the track and usually demand specific beat types or tempos to compliment the sequence.
It is not uncommon, particularly when working with other instruments to create counter melodies of voicing's the work well with a decided chord sequence. It is also another method for defining more depth and flavour within the sound of a song or sequence. Chord inversions are a good method of generating this depth ion the sound, Chord inversions are created when rearranging the notes of a chord within a sequence and playing them with the original chord (together). It is again good to experiment in order to find the ones that work best for the songwriter.