In human terms: a composer is someone who thinks of a melody and the chords to underline the melody. An arranger is someone who turns the composition into a piece for orchestra, so the drummer, guitarist, bassplayer, hornplayers etc. will know what to do. An arranger gives the drummer, bassplayer, guitarist and pianist some freedom by not exactly writing down every note, but for instance just the chords and indications for breaks etc.
In keyboard terms an arranger is an "orchestra" that doesn't know what to do, untill the keyboardplayer tells it what to do by playing chords - so in the words of Uncle Dave: WE are the arrangers.
But fortunately we players have help from professional musicians who give us templates for the arrangements, called styles. The human arranger has the help of a professional drummer, we have the help of a professional drummer playing his part as a template.
The Arranger-players have to play the melody, the chords and play the buttons for breaks, fill-ins and multipads (short sequences you can compose yourself, or you can use - mostly simple - templates). And so we can sound like an orchestra.
I like the arranger because it gives me more freedom in my playing and inspires me, because I am not playing all by myself anymore.
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drdalet [This message has been edited by drdalet (edited 11-30-2004).]