Ok so how would i go about making a script so that the "tension" music from oblivion plays in Ansestral Tombs and stops when i exit, ( like it does on oblivion)
or is there a mod which already does this?

Any ideas?
:read:

The Morrowind theme is amazing! The Oblivion theme not so much. This is absoulutley no soulution to your problem but I thought I would through it out there. :hubbahubba:

could you also do the same for Day/night?

You can start playing music from a script by using the StreamMusic command. You can't however loop a music, you will need to set a timer and restart it 'manually' each time it would end. Ending the currently played music can be done by streaming a short, empty sound file (like 3 seconds of silence).

ok
sorry i've only been doing scripting for about half a dozen months, could anyone get me started? also how would you stop the music when you exit the cell?

There can be no mod for this, because it's copyright infringement and a EULA violation to use assets from one game in another. This means no using the Oblivion music files in Morrowind, even if you have good licenses for both games.

While doing this for yourself, on your own computer, flies under the radar and nobody will ever bother you about it, discussion intended to help you do so is not something these forums will facilitate.