Let's try to explain how to obtain the sound used in the intro of one of The Who's masterpieces. Pete Townshend in the original recording used a Lowrey organ with a feature called "Marimba Repeat" that gives the exact effect of the song. Basically it is an arpeggiator-like technique: the notes on the keyboard are splitted into two parts. The first ones play down beat and the others upbeat, thus creating a rapid alternating of them.
So, in Baba O'Riley, F and C play down beat and, say, D and E play upbeat. I managed to emulate that effect using my KORG Triton with 2 custom arpeggiators and splitting the keyboard. Maybe I'll write something about it or just upload the patch. Instead, I wanna explain how to use a simple VST I coded for the exact reason of emulating the "Marimba Repeat".
First of all, you need to use some kind of modular or semi-modular VST host (the kind that allow you to "wire" audio & midi i/o the way you want) because, due to techinal issues, applications like Cubase don't allow you to use the plugin as a "MIDI Effect". A good host is Plogue Bidule.
This is a picture of the patch you have to create:
It is pretty simple: Input Device -> Marimba Repeat Emu -> VSTi (mdaEPiano in the image) -> Audio Output. The brighter wires are MIDI connections. The audio i/o of Marimba Repeat Emu are dummy and are there only to make some VST hosts happy.
All you have to do now is playing some notes to hear how it sounds like.
Let's explain the MRE interface:
It's pretty minimalistic and there's also a small help if you click on "Help/About". This is how it works: instead of playing certain notes down beat and the others upbeat it splits the keyboard in two part (much like my Triton patch does) so that the left keys play down beat and the right upbeat. It also allows you to transpose the right part of the keyboard. The "keyboard split" parameter adjust the key used to split the keyboard. "BPM" obviously sets the speed and velocity (%) sets the MIDI velocity associated with the notes.
So, to play Baba, with the left hand keep plaing F C F C F and so on in sync with the arpeggiator and with the right hand play, for example, D and E.
I made this crappy video to show my triton patch but, since the principle is the same, it gives you an idea of what you get doing what I suggested.
Download: Marimba Repeat Vst