How to turn any (pop) song into a jazz song

How to turn any (pop) song into a jazz song? Quite often there are pop songs wich get covered in a jazz style. These covers are seen from youtube to tv. Now I tried doing something like this, with for example Bad Day by Daniel Powter. It's basically a D-G-A chord progression (1-4-5), wich is quite simple. I thought, in a simple form, adding 7th chords and some altered timing, would at least give it a bit of jazz feeling. Basically it all just sounded very dissonant. Now I wonder if you got any tips or ideas on how to make a jazz cover of a song, or make it sound more jazzy. Maybe someone knows a jazzy variation on the 1-5-6-4 progression? Many thanks!

Before you replace chords with 3 or 4 notes with those with 5 or 6 notes (or even more), reharmonize a melody by applying these 2 complementary strategies recursively (i.e. each is applicable to the result of applying them, so you can do it in many passes) to chord changes: 

1) replace one chord with two (duration of 2 chords in new version = duration of 1 original chord, OR duration of 3 chords in new version = durations of 2 chords in original)

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2) replace two chords with one (sticking to one of them and make it last longer)

While you do so, make sure every step of the way, your chord substitution works with the melody: there is no one-size-fit-all replacement for something like 1-5-6-4 because it all depends on the melody. Why would you want to do 2) if you want your 'pop' chord changes to sound more 'jazzy'? That is because simplifying changes allows you to complexify them later IN ANOTHER WAY (e.g. add passing chords, etc.) to your taste. Tactics for 1) are: 

1a) Add a chord that shares 2 notes with the the current chord, somewhere in time between the current one and the next one. (where in time? you choose!) e.g. Add a minor triad with the same root if the current chord is a major triad (or add a major for a minor). e.g. Add a chord whose root is a third above or below (remembering to share 2 notes and checking if it works with the melody). For something like a G7 (in key of C), this can mean not only Bm7(b5) or Bdim7, but also BbMaj7 or Bb7 (and more... use the melody as constraint and inspiration).

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1b) Add a chord BEFORE the current one (usually between this chord and the previos chord, but you can do this even to the first chord: it just means you need to start the song sooner) whose root is a 4th below (or 5th above) the current one. Adding a so-called dominant 7th

type chord (i.e. a chord with major 3rd and minor 7th above the root) before seems to work well in most cases, but keep other choices in mind too. If the current chord is already a dominant 7th type chord, adding a minor triad (or m6, m7, etc.) before or a m7(b5) there seems to work well also (other choices are still there for you). Directions for 2) are: 

2a) Try to get rid of "passing chords". Passing chords in harmony are like passing notes in melody: they are usually in rhythmically weaker positions 'linking up' pitches more important structurally 'in the flow' (usually in rhythmically stronger positions), and they can be though of as 'diatonic' if they are within the scale in use now (or nearby), or as 'chromatic' if they are not; unlike classifying passing notes in melody, which is a pretty 'either-or' matter, passing chords can be thought of as having shades or degrees of chromaticism (i.e. the more notes 'outside the scale' a chord has, the more 'chromatic' it is said to be). Remember: you can get rid of not only chromatic passing chords, but also diatonic ones, and the chords will still (somewhat) work with the given melody.

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2b) After removing 'obvious' passing chords, less 'obvious' ones will seem to surface. Now, try to figure out what tactics the original maker of the chord sequence has used to complexify it. Was it 1a) here? or 1b)? or 1a-then-1b or 1b-then-1a? Usually for pop, as you undo this level of complexity, each section (or sections or even the entire song) can be boiled down to a very simplecadential formula (e.g. called 'authentic' or 'imperfect' or 'deceptive' or 'plagal' etc. by older theorists, 'some sort of II-V-I' by jazz theorists). As you strip away more and more chords from the original, it will sound less and less like it, WHICH IS WHAT YOU WANT.

Using these strategies involves trial-and-error (so the more you do it, the more proficient you would be at getting to a solution you like), and doing it with your instrument, score AND PENCIL helps. After you have re-harmonized a 'pop' melody using the mentioned strategies, you are ready to 'jazz it up'. By having done the re-harmonization that way, you would have already noticed what scales are implied by the chord changes and the melody from moment to moment in the song. Use those scales to construct chords with more notes to replace the simpler version by starting with the given root andstacking 3rd's up. For example, if the scale is C minor and the current chord's root is F, the chord (spelled from bottom up) can be F A (or Ab) C Eb G B(or Bb) D. Then look up the symbol for your the chord you want (from a guitar chord chart book or software or webpage etc.) and/or start considering the voicing of the chord (esp. if you are doing it on keyboard or something like it - like xylophone). But what if you have chosen chromatic (passing) chords in your solution? In that case, figure out what scale is implied by your current (and chromatic) chord, and use that instead to construct your 'more-jazzy' chord just for the moment. The reason why some chord changes sound more 'jazzy' is because they manage to make the listeners think of a key (which implies a scale) in mind by structuring phrases or sections that boil down to a simple cadential formula, but 'on the surface' ('above' that 'boiled-down' level) from measure to measure (or even from beat to beat) they use as many chromatic (i.e. outside of the

scale) pitches as possible. It is a tricky balancing act because if you CONSTANTLY use only pitches outside the key, eventually the listeners' mind would flip to deem those pitches as defining a new key. So, to created that jazzy impression, don't just go for those 'outside the key' pitches; instead, keep enough 'inside the key' pitches to trick the listeners into thinking of a key, while staying one step ahead by surprising them with pitches 'outside' of their expectations INBETWEEN. For a 'pop' audience, some tactics to do so are: 

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i) To construct your dominant chords, instead of using only major and minor scales, use diminished scale e.g. G Ab A# B C# D E F to construct G13(b5#5b9#9) for the key of C, or diminished-wholetone scale (e.g. the one starting on G has the same pitches as Ab melodic minor) to construct G13(b9#9#11) for the key of C. For chord constructions of non-dominant chords (e.g. tonic, etc.), using melodic minor or harmonic minor scales allow for more opportunities for 'more jazzy sounding' m7(b5) [i.e. an 'inversion' of 'minor triad add major 6th' chord] or mM7 [minor 3rd and major 7th above root] chords (and similar chords with more notes). 'Pop' songs seem to use quite a bit of dim7 chords (and similar chords like 7(b9)) too, so it is up to you to decide if using them makes your song more 'jazzy'. ii) Apply 'tritone substitution' to your dominant chords (which can be thought of a frequentlyused and formulaic application of strategy 1)-then-2) or 2)-then-1) ... but that is really stretching it ... ). e.g. replace G7 in the key of C with Db7. Not enough dominant chords there to do this? Backtrack from you current attempt to 'jazz up chords by added more notes to them' and go back to applying strategies 1)&2) more in order to put more dominant chords there in the first place! (for this purpose, let's just say any chord with a major 3rd and minor 7th AND going into a next chord whose root is a 4th above or a 5th below is a dominant chord). This is quite doable for many 'pop' songs. If the melody allows it, you may even be able to simplify-then-complexify your chord changes to a point for 'Coltrane substitution' to be applicable (for 'pop' melodies, this is less often doable than 'tritone substitution', but far from impossible). Needless to say: Coltrane sounds REALLY jazzy!!!

Boiled down to: occasional use of secondary dominants, diminished passing chords, and possibly altered tensions on some of those dominant chords.

Be careful with the Maj 7 on I chords (ie DMaj7), which will quite often conflict with the root (D) played in the melody : you tend to get a b9 interval between the 7th (left hand) and the root (right hand) with sounds very bad. In that case, substitute DM7 with D6 which will sound smoother. The IVM chord (GM in our case) can often be replaced with a IIm7 (Em7), which will sound nicer than GM7 here (for the same reason: it avoids a b9 with the root of the chord). The AM chord can generally be played as A7 without problems.

If you stick to these substitutions while playing the melody, then you should not have too many problems and end up with a jazz feel. Then when soloing, you get access to the whole thing, including tritone substitutions (Em7 -> Eb7#9 -> DM7 and such).

Learn jazz reharmonization techniques. You might pick up a book like "Reharmonization" by Randy Felts, or even "Harmonic Foundation for Jazz and popular music" by Jimmy Amadie. You got to reharmonize it using chords that are outside the key, or at a minimum chord tensions that are not in the key of the song. Use secondary dominants.

Simple: Adding sevenths (4-part harmony), specially on I and IV (maj7). If that's not enough, adding 9s,11s,13s