where can I find out about traditional dance music and nightlife. I will be there in October in Athens and the islands.
It depends a bit on what you mean by 'traditional'.
Some of the tavernas in Plaka, the main tourist area in Athens, have music and dancing put on mainly for tourists.
Outside of that area there are a number of clubs that play rembetika, roughly the Greek equivalent of the blues. This is a good starting point for these
The other common music is laiki, roughly the equivalent of folk. A number of restaurants have this on a fairly informal basis ie just a duo or trio playing sat at a table. In Athens the Sigalas, in the block opposite Monastiraki metro station, has recently reopened and generally has people playing. It's a good place to eat anyway, if you like traditional eating places, and gets a mix of tourists and locals.
Its difficult to give much advice about islands. It depends which you are planning to visit.
If you are traveling alone, then you will get plenty of "nightlife" invitations.