Perhaps it might be helpfull to look back to a time before accordions, when keyboard instruments had little or no volume control and much dance music was played on instruments that inherently do not have any dynamic range... like bagpipes.
If one cannot create lift emphasis by changes of loudness then there is an almost complete reliance on rhythm and measure. So, the way one plays the melody has to be addressed first. A steady 'external rhythm'( the length of each bar etc) is of primary importance, of course, but it is the 'internal rhythm' that can give lift and grace to the music. That subtle lengthening and shortening of notes within the bar, the gaps between , the use of grace notes to emphasis rhythm.
Unfortunately Staff and ABC notation is not subtle enough to give an idea of Internal Rhythm and of course the style of emphasis varies greatly between genres and individual musicians. Perhaps the best way is to listen and these days it is easy to take a recording and slow it down to a speed that one's ear can detect the differences in note length. Listen carefully for the way a musician 'weights' the rhythm by altering the note lengths.
I lived for many years in the west of Ireland, beyond the guitar belt, where sessions ( not gigs) usually consisted of fiddles, flutes, concertinas and whistles. Playing with the OLD people was an education in lift. That, now passed on, generation had played great dance music with out the aid ( or hindrance) of rhythm strummers. In comparison, when I listen to the younger crowd, who have grown up in sessions where rhythm control is given to the guitarist, I often detect a flatness to their melody playing. Now I'm not saying there is anything wrong with having accompaniment, just not to use it as a crutch.
Now, in France and playing mostly French dance music I notice that those novice bands , which often get a chance for stage experience during a Bal, exhibit a timidity which results in a very flat performance. Usually they are playing a tune 'at the same time' but not together... they are looking for the measure, the pace, not able to lock-in together .
I am fairly new to the accordion and really enjoying the possibilites, especially in dance music. After many years of playing the English Concertina, which has no dedicated rhythm section and relies on the player to keep the time firmly in their head, or foot, it is so much fun to realise how much can be done between the left and right hands on the accordion.
PS. just a quick example of this note length adjustment; in the playing of 6/8 Jigs there are 6 quavers to the bar, in two groups. If one ascribes note lengths in numbers to each of these the bar could look like 5-2-3, 5-2-3. So, the first note is longest, the second is shortest and the third is somewhere between. This is just the way I think about it and the actual note length values may differ, from player to player. This is what is known as 'Gimp' in Irish Trad Music . The same thing can be done with any dance measure to aid lift.
