good points made between the T4/T5....Yamaha doesn't make BIG changes model after model in arrangers which sometimes leaves a bad taste in peoples mouths as if they are being lead on minimally and financially I hope that changes with T6....sure the brand loyal will always upgrade but are they really happy....let's see what this mext offering brings...I hope they wake up and make this the best NEW Model arranger they have ever produced....

And what about different sounds? They are "software", if you will, but the most important part of the instrument.

Just listen to the examples of saxophone, muted trumpet, trombone and pipe organ Mikem posted, beginning at 0:50. Listen with headphones!

https://youtu.be/KaaijjzD_aE

I hear substantial improvements. The saxophone is more direct, muted trumpet and trombone were only "Sweet" voices in T4, but SA2 voices in T5, with the effect that they play far more expressively. The pipe organs are very different, too. The T5 one reaches the realism of Hauptwerk samples, especially with the bass registers played with left hand.
Of course these all are differences between "already good" to "very good", not from mediocre to very good.

The sounds within the MIX vs solo is whats important to me when I perform and yes they are fantastic...If they never change the sounds or styles again on today's TOTL/MOTL I would be very happy at what we have in the way of styles & sounds not to mention besides all that you could also edit, tweak and create your own too, no matter what you do it will always still be an arranger, if you used arrangers since the beginning like myself you know how far they have progressed,.....Big Changes in features, technology, navigation, weight, design, it's where their efforts need to be addressed IMO.

I've witnessed the development of auto-accompaniment instruments beginning with a Yamaha Electone in 1985 via Gem WS 2 in 1991 to BK-7m and BK-9, a span of 30 years, too. But I also know that auditive perception is changing. What sounded spectacular in 1991 sounds cheesy nowadays, so Tyros 4 sounds won't be good forever.

1985?...... Ive been performing on keyboards since 1964 on stage.....and let me tell you for almost 20 years an arranger KB wasn't even heard of funny how we try to emulate the older sounds for many reasons,......yes the sound and technology has changed but the gap is slowly getting much closer..still nothing beats the real thing.

Well, I know that I'm one of the relatively younger forum users here, roughly the same age as Bachus and some others, but as you say before 1985 arrangers didn't exist anyway, so 30 years is certainly a very long time span and enough to have experienced dramatic changes in technology from FM sound generation to samples etc. I think at least for the affordable range of instruments the fastest development took place between 1986 and 1999. Since then there has been a certain slowdown.