Ugen for selecting and merging nested Array Data

hey, is there a Ugen available which i could use to select and merge multiple subarrays from a nested Array.

like:

array = [ [1, 2, 3], [4, 5, 6], [7, 8, 9]];

select [0, 1] -> [1, 2, 3, 4, 5, 6]

thanks

Why exactly does it need to be a UGen?

a = [ [1, 2, 3], [4, 5, 6], [7, 8, 9]];
a[0] ++ a[1] // -> [ 1, 2, 3, 4, 5, 6 ]

If you want to statically select audio channels you can do this:

(
{
	a = [ 
		[SinOsc.ar(), Dust.ar(100), SinOsc.ar(SinOsc.ar(1).range(100,150))], 
		[WhiteNoise.ar(), LFSaw.ar, LFPulse.ar], 
		[Blip.ar(), Impulse.ar(), Formant.ar()]
	];
	
	//(a[0] ++ a[1]).sum/50;
	(a[0] ++ a[2]).sum/50;
	// a/50
	
}.play;
)

(remove .sum to get the array of channels)

If you want to cross-fade these channels then probably you are looking for something like Select.ar()