Any sound you create with the on board edditors...
You can go really crazy on some arrangers like the pa4x where it comes to creating your own sounds... even the Genos is okay for that...

The same discussion could be about todays organs and stage piano’s ..

The power of an arranger keys these days, is that its a synth, which allows you to create both authentic sounds, as well as emulating sounds...

If you want to cattegorise all the above instruments, they are synths. Which means an instrument that allows you to create your own sound... hench, synthesis.

A simple question can’t be stupid..
but a question based on someone’s reasoning can be stupid, espescially when the question itselves holds much of the answer the questioneer wants to hear..

Anyway, i should rephrase.
There is no use in discussing this, as an arranger is an arranger..

Why do we humans allways want to label things?

(disclaimer: no wikipedia used - posted actual memory)

When I was studying music (at Temple in Philly) in the 70s, they taught us that there were 4 groups of "instruments". They were:
Percussion - things that need to be struck to make sound (piano is part of this group)
Woodwind - things that use wood to manipulate air to produce sound (early flutes were made of wood, so they are in this group)
Brass - things that use brass to manipulate, and amplify air to produce sound, and
Strings - obvious description.
My first question was ... "What about a Hammond organ?" Is that NOT an instrument? The books at the time all said no, because it didn't move air. The tone wheels use electricity to spin, and create a sine wave that is sent to an amplifier, and the "sound" comes from a speaker, thereby not creating the tone, itself. Without a speaker, and amplifier, it is not capable of moving air. Early pump organs, may complicate this argument, but the simple truth was - in order to pass that course, I needed to say that there were only 4 groups of musical instruments.

I wonder what they are teaching today's music students? With all the cyber, and virtual sonic choices we have - what's real, and what's "memorex?" (there's an OLD memory, huh?) Food for thought.

To me the definition of 'arranger' is some form of orchestrated auto-accompaniment. Usually with chord recognition that augments or complements the keys being played in real time. I wouldn't call the Roland DisCover 5M an arranger, nor Band in a Box software. But the tiny Yamaha QY-100 "walkstation" qualifies as an arranger IMO, because it has "patterns" (styles) and real-time chord recognition.

None of these are musical instruments by your definition, because they don't produce an original sound. Most Korgs and the Casio MZ-X500 have synth engines that allow a user to synthesize an original digital sound using layers and LFO's. They are true synths, that also happen to have a complete arranger feature set.

Some mechanical band organs from the early 20th century might be the first arrangers. They had paper music rolls, and some of them had keyboards for real-time play. These things definitely made their own sound, enough to fill a room!

So I guess what I'm saying is that being an "arranger" isn't sufficient to make something a musical instrument, but neither does it prevent something from being one.

To further muddy the water, there are keyboard-controlled devices like the accordion which are definitely musical instruments (free reed aerophone.) An accordion has robust auto-accompaniment capability, especially the more sophisticated models that have bass-to-reed couplers, etc. But no one would classify them as arrangers!

To be fair, the textbook that I studied in college was probably written before electricity became widespread in the world. There is so much grey area concerning audio, digital property, and such that we may need to be very open to some new terms in our lives. When I was teaching school, and short 4 years ago - some of my kids all thought that being a "YouTuber" was an actual job. Looks like they may be on to something. Sounded strange at the time, but there are people making a living doing videos in their homes. Go figure.

According to Wikipedia...”A musical instrument is an instrument created or adapted to make musical sounds. In principle, any object that produces sound can be considered a musical instrument”.

In my 5th semester of Music Theory, one day our professor told us to begin making music with whatever tools we had. The class was slow to respond. A couple people started tapping pencils on their desks. One guy grabbed the trash can and started bongo'ing on it... someone got on the board and reluctantly started scraping chalk... Several folks were just taking it all in with wonderment. Then the professor went to the blackboard and wrote "Everyone must participate!" Then, some people started raising their desks 2" off the floor and dropping them back down...one guy started opening and closing the venetian blinds. Several people started clicking their fingers while others clapped. Me and another guy had a rehearsal to go to so we departed the room - and on the way out we added to the music by slamming the door so hard that it blew ceiling tiles loose and jammed the door. That was the last time we did that exercise. But it was musical!

^ I'd call that a jamb jam.

The maintenance guys had to come "unjam" the door and several of the other students (had been stuck in the room) came late to our rehearsal due to the door being stuck. Oddly, we were never asked about the door slam - most likely because the noise of our experiment took place directly over the music department chairman's office. Suspect he was happy when our tune ended.