The arranger-function of my keyboard is mostly used in my "home studio" where I write new songs. I use the arranger there for a quick "feel" of the song (without having to play all the parts first, losing the idea in the process and ending up with no song at all or something completely different than I intended to do

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I never perform as an OMB, but who knows what the future will bring

For now, I use the keyboard on stage with a band (thus playing the typical keyboard-parts such as piano's, organs, string"carpets" etc and an occasional solo) and in a homestudio-environment together with a guitar player where we play, have great fun and sometimes even record something

The reason I started using an arranger in the first place was not the arranger-part of the instrument. At that time, arrangers (in the pricerange I could afford) were the only instruments that featured "real life" instruments. I never was and never will be interested in the bleep bloops of the typical "synthesizer". I wanted true piano's, organs, guitars, brass, strings... and found them in the Roland E-15 (1992). The arranger function of that instrument was considered to be "a nice extra" but we never really used it much.
Over the years the arrangers got better and better, and now, being able to alter styles, it becomes a very usable function.