> Thanks guys I will be having a bash at this tonight. What software would you lot recommend for music making ATM I'm using lsdj and lgpt but want to involve The Atari
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What 505 said.

With a note, however, that we don't actually know what amount of RAM You have in the 520.

If You have only stock 512Kb, then MusicMon will not work (I've just checked it out). You'd need at least 1Mb.
But worry not - there is a special version of maxYMizer that works on 512Kb machine.

Still, I suspect You should have 1Mb after all.

________EDIT_______
If You'd prefer to use the Atari as a digital background for Your GameBoy, then You might also take a look to this small article -
http://www.atarimusic.net/forum/topic?f=124&t=107

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I have had some bad experiences with floppies made with Windows running on an ST.  Rainbow TOS seems to be the solution.  Check the about screen: http://www.larwe.com/museum/img/tos_about.gif

If it says 1985, you have an older (stock) TOS.  Rainbow TOS will say something like 85, 86, 88, 89.

you can use normal floppys, block the hole at the upper left corner, and format the disk with this parameters
format a: /t:80/n:9

now they should work

You can do it with windows too ! (if you have XP or older !)

Talking about SDs...don't forget about Satandisk or Ultrasatan !!!

now they should work