Jammin in ...

I wrote this offline as its going to be a long one.

If the guitarist/whomever shouts out "I am in C" then the key is Cmaj. This means that there are 8 notes that spring to mind (all the white ones on a piano). So…

C 1st
D 2nd
E (maj 3rd)
F 4th
G 5th
A 6th
B maj 7th
C octave

However once you know the rules you can choose to break them. So you can have 12 notes to choose from in your progression. However that’s just the C chord, there will probably be others. The most common progression is I VI V which is 1 4 5 which is C F G. If someone says 12 bar in C (they will probably say A but nevermind) then it will use those chords like this I VI I V VI I it may have a turnaround (V) at the end. Try to listen to the changes and read this excellent thread by lump http://www.talkbass.com/forum/showthread.php?s=&threadid=20754

Another common chord in the progression is the relative minor for C it is Am which is 3 down so for D it's Bm etc. Ok back to what you play. Guitarists use open string and keyboards have banks of 2 and 3 black notes so patterns change. However play a scale (properly) on a bass and if someone wants to change the key (not maj to min though) you play the same pattern in a different place. So C major scale…

Place the longest finger of your freting hand on the A string (2nd biggest on a 4 string) at fret 3. Now with your little finger play the D on the same string (yes it hurts) now play the E with the forefinger on the D string (at fret 2) and work the rest out. You should end with the little finger on fret 5 on the G string (skinny one). If this is too basic for you, sorry.

RE what to play, I've been trying to work that one out for 20 years. Listen to some records (CD's) make sure there is a variety of styles. See or hear how they constructed them Don’t just think 'up' some lines go lower than the root note. There are some arrangement devices that work well. See below for some examples.

Pedal-this means that there is a chord sequence say C F G C but you play a C or C based riff all the way through. Do this in the verse and move around with the progression on the chorus or vice versa (make sure you have a chorus pedal for the chorus-this is a Talkbass standing joke I am so good to you).

Decending bassline over one chord-no more to be said.

Slash Chords-sometimes arrangers (or you) will choose to use different roots so Instead of playing C D Em like a faithful puppy with the others you play C F# E. It would be written on a chord chard as C D/F# Em. Guess why its called a slash chord.

Finally be creative and just play, move your fingers about and see what happens. Keep the good stuff and say to mr leathertrousersandbighair "Ive got this riff in C(whatever) can you play guitar to it?"

Learn to remember songs rather than staring at paper. Learn how to work things out by ear. Learn to read tab it is useful but remember most tabs are inaccurate (which is where your ears come in). Learn to read music. I have not done a reading gig since 89 but I have one in Feb so its back to the bass clef (bottom line is G )(I think) for me.

Hope this helps and keep working at it.

All the above is how I see it and will be proved wrong by at least 2 posters.

 

CS's post is WRONG WRONG WRONG! Just kidding! Excellent advice.

Welcome to Talkbass KINGKONG!

The only thing I'll add to CS's post is regarding the other part of your question, where the people you're jamming with say "I am going, C, D, G....".

It all depends upon what type of music you're playing, but if it's any standard rock or blues, then they're probably playing dominant chords there. So, they could say, "I'm playing in C" but what that doesn't do is tell you what other chords they're playing. The good news, is that as long as those chords they're playing all naturally appear in the scale of C major, (for more on scales, Click ME!), then your bass line will sound fine. Often, they're playing the dominant chords, so they won't all be diatonic, which really isn't a huge problem, because at this point, even if you're playing diatonically and they're making slight modifications, it probably won't be extremely noticeable or even sound all that bad. What you'll also find quite often, is that they'll probably be playing in your standard minor pentatonic or blues scales, (minor pentatonic with a flat 5 added). So, becoming familiar with your blues scales can definitely help.

Back to the "I'm playing C, D, G" stuff. Like I said, there's a good chance that they're playing dominant chords, C7, D7, G7. You can use the method of introducing the blues scale I mentioned above, but you can also play a lot of chord tones there, with some chromatic additions, or not, and it will also work. So, remember the chord tones would be C7 (C-E-G-Bb), D7 (D-F#-A-C), G7 (G-B-D-F). So, let's say they're playing a phrase like:

| D7 | G7 | C7 | C7 |

With this phrase, you can start out real simple by playing chord tones for each bar. Your bassline doesn't have to involve the whole scale. Play with rhythm to make it interesting and dynamic. Play with the chord tones to see how they relate to each other. (Example: At the second bar, your G7 has B as it's third, which can lead right into the C of the next bar, the third bar, which is C7).

For extra experimentation, you can add the 6, (the dominant chord being the 1-3-5-b7). So, C7 (C-E-G-A-Bb), etc. etc.

 

FME, that could mean 'anything'...usually the FIRST chord/note will be a "C".

*** Chris & Jazzbo have offered what should be expected when somebody hollers out the Jam du Jour's "key" ***