Song keys, chords, and constructing a bassline

[Hullbert]

Hi everybody,
While working out the bassline for one of my band's songs, I came to a music theory impass with my guitar player. The song we are working on is in the key of Am. During the solo, I play a run that includes the note A sharp (the run is constructed as a C7 shape). The rhythm guitar player is playing a Cmaj chord at the same time that I'm doing this run. The chord progression of the chorus is: G-D-C-D-A
Here's where the problem comes in, the guitar player told me that I could not play the A sharp in that run because it's nowhere in the scale of Am. I said that it was permissible because the rhythm guitar player is playing a c chord and that A sharp was part of the C7 chord (which I wanted to add to give the progression more of a blues flavor). He then said that it didn't matter what chord was being played, that the bass had to continue playing only the notes found in the Am scale. His analogy was that when writing a solo, he could only play notes in the Am scale-regardless of what the chord progression was doing at that moment.
I apologize if I haven't done a good job of explaining the situation, but here's my basic question:

Can bass lines only include notes from the scale of the song key, or can the bass play notes outside of that scale?
Thanks so much for any help anybody can give me on this situation.

[santucci218]

you can always add notes outside the scale. as i always say, there is never a wrong note, just bad choices! sure it may not sound great to your guitarist, but to your ear it may sound like the perfect note. dont let the guitarist hold you back from expressing yourself on the instrument. you should be expressing yourself, not him.

[uturnbass]

no, you don't HAVE to play notes that fit in the Am scale, you could play any note, but the notes that sound best fit in the scale.
But, some notes that aren't in the scale add some cool tensions and sounds to a lick or run.

[improvpwnd]

I believe its more of an issue of which beat of the measure that note is played on and the duration of the note. If it is played on the first beat of the measure it probably won't sound great (usually should be the root note). Other than that, if the note is played as a pick up to the next note (maybe as a eighth note or quicker, assuming it is a walking-type bassline) it should sound fine. Either way, rock on..

[Hullbert]

First, thanks for the responses!
Second, the A# is definitely used as a pickup note in a basic blues boogie riff. In other words...C-octave C-A#-D.

I'll definitely keep working on this-who knows, I'll probably end up rewriting the whole thing before it's over.

Maybe my problem is that I know enough theory to be dangerous, but not enough to be good at it.

Thanks again to everybody for taking the time to answer.

[Depth_Charge]

Mate I'm pretty clueless on theory. For me, what sounds good is always my first choice when constructing basslines. Thankfully when my guitarist screws his face up and asks "What are you playing there, I'm on A" and I quip back "D", I usually get "Oh. Yep. Thats in the chord. Cool. Keep playing that then, I just didn't like it."

From the explanations I've read in this thread, it sounds to me that your guitarist is the one who knows enough theory to be dangerous, or thinks he knows more than you, IMH and uneducated O.

[DocBop]

As others are saying you don't have to play notes from a scale, but if you don't you need to know what your doing. The A# is a minor 2 or minor 9th depending on the octave. So to make it work it needs to be on a weak beat or used as a passing tone or approach note. Bottom line you have to be careful.