Well, I have played bass longer than keyboard, now play mostly keyboard. Also a bit of autoharp and tremelo harmonica. Used to play clarinet and sax. I learned to read music when in high school band - and I don't usually play anything by tab. Used to work on church (electronic) organs, play a bit of organ.
Tab is a simplified system designed for guitar and bass, particularly for those who cannot read regular music. In tab, the notes (or chords) are shown as little stick drawings of fingers on the fretboard. So - the first thing you need to do if you read music or play by ear and want to use tab is to get a tab chart, figure out what chords that each tab symbol means (unless the chart you are reading also has the chords)
Once you know the chords, you just make a progression like you would normally make it.
A difference - some progressions that are EASY on a bass are not easy on a keyboard (same way - some that are EASY on a keyboard are difficult on a bass) - that's just because the two instruments are made different.
What it will mean is that, if you have both bass and keyboard in the band - ONE of you needs to lay out on the bass, because you are very unlikely to use the same progressions.
Our praise band has one very good keyboardist (not me), she has learned to comp and chord mostly above middle C, some notes below, but NO strong bass line, except when she is working solo. I play a Kurzweil synth and a computerized Hammond organ/Leslie emulator. So, a lot of the time on the faster music, I'm filling in the bass part, usually either with a bass sound or using low bass from a concert grand piano sound. Sometimes, we do a song that just calls out for a real bass, and I bring either my RD Artist or my Les Paul 5-string, and switch to bass for the song. I also comp occasional chords with the Hammond.
On the slower stuff, I usually do strings, pads, flutes, other orchestral instruments. Another thing - the more people in the group, the less each one needs to play. There is more of a beauty in music that has a bit of silence occasionally than when everyone is trying to shred at the same time! In instrumentals, most of the lead is from the keyboard or our guitarist.
When I am following God's lead - my playing is to complement worship and the other musicians - NOT to raise my own profile. I used to also play some out in the world - but FOR MYSELF I now believe that music is my God-given gift, a talent. I want to USE my talent (and see it multiply), I don't want to not use it (and be rebuked) - and especially - I don't want to be pimpin' out God's gift, playin' the devil's music!
Jim
