It's time to move on. Yes they may spread rumors and trash talk you, but life goes on. A guitarist and I quit a band to form our own and had death threats made against our lives. We're both still alive and have been long forgotten by the "rock stars" we left behind.
Unless you sold yourself to them when you joined the band, I'm not sure how they can ban you from playing anything but the root notes. The "rock star" guitar player/singer from above, wrote a song and gave me the freedom to write the bass line for it, so I did. When we played the song, he stopped us in the middle of it and turned to me and told me I was playing it wrong. How can I be playing it wrong if I wrote it? I was defining the chord as a minor by adding the flat third, since all he played were power chords, root and fifth. Since it sounded minor, he figured it was wrong, but IMO, it suited the song better than the root would have.
Are they forcing you to buy another bass so the original bass player has something to use for the big gig, since you can't play 2 basses at the same time. If you love the bass you have, don't get another one unless you have a proper use for it, like a different tuning or something like that. Otherwise, you're going to end up sharing it with the old bass player. If you don't need a different tuning and just want a new or different bass, trade your old one in.
It's time to move on, put up posters looking for a drummer, connect with a drummer and then find a guitar player, then a singer and you'll have your own band. Create your own vision and give the other band a run for their money. You'll be happier and have the freedom to grow as a player. A friend of mine says "If you're not growing, you're dying." and in your case this rings with some truth. Best wishes.
Unless you sold yourself to them when you joined the band, I'm not sure how they can ban you from playing anything but the root notes. The "rock star" guitar player/singer from above, wrote a song and gave me the freedom to write the bass line for it, so I did. When we played the song, he stopped us in the middle of it and turned to me and told me I was playing it wrong. How can I be playing it wrong if I wrote it? I was defining the chord as a minor by adding the flat third, since all he played were power chords, root and fifth. Since it sounded minor, he figured it was wrong, but IMO, it suited the song better than the root would have.
Are they forcing you to buy another bass so the original bass player has something to use for the big gig, since you can't play 2 basses at the same time. If you love the bass you have, don't get another one unless you have a proper use for it, like a different tuning or something like that. Otherwise, you're going to end up sharing it with the old bass player. If you don't need a different tuning and just want a new or different bass, trade your old one in.
It's time to move on, put up posters looking for a drummer, connect with a drummer and then find a guitar player, then a singer and you'll have your own band. Create your own vision and give the other band a run for their money. You'll be happier and have the freedom to grow as a player. A friend of mine says "If you're not growing, you're dying." and in your case this rings with some truth. Best wishes.