After struggling trying to understand modes these last few weeks, i think i have finally grasped them after looking through lots of resources (including virtually every single thread here on TB since 2000 that have "modes" in the thread title). The only thing that i'm not certain about now is the practical application of parallel modes when it comes to chord progressions....but that will be cleared up soon, i hope. Here, i want to explain modes as i understand them in the hope that it may clarify some things for some people. I know modes creates a lot of confusion. Rather than try to explain modes as if they exist in a vacuum, i want to explain them in the context of chords and chord progressions because a) that's how i learnt to understand them, and b) i think it's essential to provide a practical context when explaining things so that the concept of modes doesn't seem like it is 'up in the air'. Most of the time, people seem to just explain the concept and theory of modes without a practical context of where they can be used in practice, and that's why it's taken me weeks to be able to understand them. Chord progressions Up until recently, i thought that chord progressions started and ended on the parent key chord (ie I). For example, the progression I -V - IV -I. If we take the key of C major(ie C D E F G A B) and look at the chords within the family of C major, we have: C major(I), D minor(ii), E minor(iii), F major(IV), G major(V), A minor(vi), B diminished(vii). So the progression I -V - IV - I will be C - G - F - C. The reason why Dm, Em, F, G, Am, and B diminished are all in the key of C here is because we are only dealing with the root, 3rd, and 5th notes of the chords. They, afterall, are what makes the triad of a chord. For example, the triad of G is G B D and the triad of F is F A C. All notes there are in the key of C. Playing notes in a bassline other than the root, 3rd, and 5th If we are only going to be playing the root, 3rd, and 5th notes, there would be no problem in just playing the root, 3rd, and 5th notes in the Ionian scale(ie major scale) for C, F, and G in the progression. However, what if we also wanted to play the 4th, 6th or 7th note in G or F major to spice up our basslines, yet still be in the key of C? If for example, we played the major scale of G beginning on G, we would find that we have the notes G A B C D E F#. Oh dear, we have a problem. F# is NOT in the key of C major. This is one of the many ways in which modes come in very useful, of which i'll address next. Staying in key on different root notes other than C We know that if we play the C major starting on C we get the notes C D E F G A B C, so what if we wanted to play starting on G or F but still be in the key of C major? If we play the major scale on D, we get the key of D major: D E F# G A B C# D. Hmmm F# and C# are not in the key of C, so lets try something else. Ok, let's play the Dorian scale starting on D - what do you notice? We notice that we play the notes D E F G A B C D. When we play Phrygian on E, we get the notes E F G A B C D E. Likewise for Lydian on F we get F G A B C D E F , and Mixolydian on G we get G A B C D E F G. So we know that if we play the Mixolydian mode on G we can play all notes in the key of C major and still be in key. Likewise for the playing the Lydian mode starting on F. It was at this point that i understood what modes are, but i couldn't really see any way of how or why they should be used in a practical manner. But after much reading, it was the following information which answered those uncertainties for me: the tonal centre of a chord progression. The tonal centre of a chord progression One thing must be noted is that the chord that the progression starts and ends on is VERY IMPORTANT. That is the tonal centre. So how do modes come into the equation and how can we use modes to spice things up? Well, this is what took me a while to get my head around. Not because it's difficult to understand, but because of the way they tend to be eexplained. INSTEAD OF HAVING C AS THE TONAL CENTRE, WE CAN START AND END THE PROGRESSION ON THE (for example) 2ND NOTE OF THE KEY OF C TO GIVE THE PROGRESSION A COMPLETELY DIFFERENT FEEL. THE MAIN POINT HERE IS THAT D NOW BECOMES THE TONAL CENTRE RATHER THAN C. If the tonal centre was E, the chord progression would have a different feel again. The same for F, and so on. The notes in C Ionian are C D E F G A B, whereas the notes in D Dorian are D E F G A B C. Exactly the same. It is still in the key of C! The original progression was C Ionian - G Mixolydian - F Lydian - C Ionian. So how does this get changed now that we want to change the tonal centre from C Ionian to D Dorian? Very little, in fact. Instead of the progression being I - V - IV - I, it now becomes ii - V - IV -ii. In terms of chords, it is now Dm - G major - F major - Dm. Play the progression C major - G major - F major - C major, and compare it to Dm - G major - F major - Dm. BIG difference because the total centre is now D minor instead of C major. And everything is still in the key of C major. How do the modes change? Now they are D Dorian - G Mixolydian - F Lydian - D Dorian. Neither the G Mixolydian nor the F Lydian change. Whatever notes from D Dorian, G Mixolydian, and F Lydian you decide to play, everything is still in the key of C major(this is now the parent key). The new progression is now in the key of D Dorian rather than C major(ie C Ionian). C major is the parent key from which D Dorian is derived. Summary of the practicality of modes 1) Using derivative modes to play on a different root note and still be in key 2) Changing the tonal centre of a chord progression. 3) Somewhere within a progression, you may decide to play in the Phrygian mode to give a solo a Spanish feel even though one or 2 notes may not be in key. Rules are meant to be broken, and many bassists seem to do this, but i'm not sure how it works yet. 4) Parallel modes. Not sure about the practical application of these yet, although i know what they are. Hope this can be of help.