Multiple devices

I just wanted to know if i have to purchase symfonium twice to use the app on two devices ??

(both will be using the same google account )

but what would happen if i change google account in one of the devices ??
is there some place where i can read about this ?? i tried to find info about this on the site but was unable to find . So , any help is appriciated

As the FAQ explains license purchased on Play Store are tied to your Google account.

If you remove your google account then you loose the license.

ohh ok , so i can use it on both of devices (same google account) simulteneously, correct ?

yes as all apps on Play Store.