scales changes

ok im working on a song and i was thinkin of havin a rythm that changes from A natural pure minor to A phrygian and i was wonderin if there is any easy way to get bassline for it like a scale that you can play behind both of those scales like i dunno a pentatonic

also is that scale change crappy cause im kinda just starting out this whole scale weaving thing with writing my own stuff

Pentatonic could be used sure.
But to be honest I have never made a piece saying to myself, I'm gonna switch scales on this, it happens or it doesn't.
Don't force it.

Understand that music is not just putting gimmicks together.

well no i was learning my scales and this tiny rythm came to me on those two scales and i thought well i gotta practise scale changes but i wanna know if i could do it with other instruments

plus if there was a scale that could i could jam to my hearts content :D and hopefully get somthing

Agreed you should let it come, however learning how won't hurt, as long as you use it as a tip, not as a steadfast rule.

I am slightly confused as to what you're asking for, so if this doesn't help please reiterate your question.

To change from A minor (Aeolian) to A Phrygian in a smooth manor you may wish to look for similarities between the two scales...
If you don't want to experiment yourself, here's what you may find,
the A minor chord from Aeolian coincides with A minor from Phrygian, as does C Major, Em FM. All this is doing is mapping one scale on top of another to see which pieces line up. Try it with the two scales to discover notes which can be toggled between A Aeolian and A Phrygian as to make a phrase to connect the key change and help it flow.

well i wrote this riff that changes between those two scales while practising but i want a simple bassline that can be played behind the guitar so i wondered if their was a specific scale or if i'd just have to use only certain note in those two scales which doesnt really give a specific scale and i don't like the idea of not being allowed to play certain notes in a scale your playing in so i wanted a scale which would be able to be played as a backing to the riff and not clash with it if you get what i mean

and i checked the pentatonic scale is perfect =D