I highly enjoy playing the guitar on my free time, but I lack a singing voice and I'm not in a band. Therefore, it is instrumentals I am most interested in learning. I've learned a few over the years in the genres blues, rock, folk and classical and occasionally played them live.

Lately, I've started to become very interested in composing something myself completely from scratch. What I mean is, I don't necessarily want to start out from any of the traditional chord sequences from blues, rock or folk but rather try to find something fairly unique. I imagine my first humble composition will set out from a chord sequence of my own construction and then embellished from there. Perhaps a chord-floating-into-melody-and-back kind of deal, along the lines of "Little Wing" or "Under The Bridge"?

I am very confused over how to get started. I guess what I'm most insecure about is how to find a good chord sequence for the song, which I guess is typically square one in the composition process? After that, I can imagine embellishing away by modifying chords, adding coloring, changing voicings, breaking chords apart, making a melody crystallize and so on, but it is my insecurities about how to come up with the underlying chord sequence which really holds me back.

Here is some kind of attempt to express what I'm wondering:
1. Is it a good/common starting point to just try around with simple majors and minors as a first attempt to establish some kind of first draft, and then move on to changing some of the chords into variants such as sus:es, 6ths and so on? Or might that be a dead end?
2. Is it wise to just start completely from scratch? As I understand it, chord sequences that "work" as a basis for songs could be of just about any nature, but perhaps there are some typical standard approaches and general pointers as to how to structure them, some universal truths about what "works"?
3. Sometimes when studying chords for existing songs (something I know I don't do enough) I find myself wondering "why that chord there, on what basis did the artist decide on that one in particular?", "why does it sound good?". This usually happens in situations when I see a really strange chord somewhere. I'm just confused, where does a decision to use an obscure chord come from? A calculated choice from an extensive mental library of chords or just a random experiment that just seems to work out?

Sorry for the messiness of the above, but I'd greatly appreciate input and tips from anyone with some experience in composing their own songs. Answers referring to any of the specific questions above or just general suggestions, tips for books or websites or accounts of your own strategies in composing songs and creating chord sequences are very welcome. Thanks!

I'm in the same place you are. no band or voice. When i try and right instrumental songs i try and think of the mood that i want the song to be. Then i pick a scale that fits the mood and put it into a key. then for chords i use variations of the chords from the scale.

The other way i do it is find a riff that i like then figure out what key it's in and go from there. mostly its just trial and error.
hope this helps
First off, do you mean instrumental with just your typical guitar, bass, drum, or do you mean instrumental orchestra, because I have more experience with that, or chord/melody/solo for solo guitar is probably my biggest strong point, which brings me to your next point.

Often times those "obscure" chords come from reducing all the notes a whole band is playing, including the melody notes, into a chord. What I mean by this, is if we look at a big band song for example, and analyze the notes that saxes, trombs, trumpets, ect. are all playing at a given time, often boil down to 4 or 5 notes making up chords such as b7#5th chords, or all those wonderful little Tertian chords (your 9's, 11's,and 13's), and many times the reason for this (especially in Jazz music) is because your typical A, G, and C chords don't work for an entire song. Sure their used, but on your cadences, turning points, ect. other notes need to be utilized to mimic either the melody, or if there was a singer in the original version of said instrumental, these notes usually end up changing the quality of the chords from say your typical A, to maybe an Am7#9 for example. Basically what I'm saying is its adding more "colors" to your music, and rather then hearing your C-G-D-C progression which is very bland, adding these other notes often times adds a "voice" to your music. You can hear the melody through chords in a sense.

Hope this doesn't all seem like bull shit, I'm in the same position as you, and often times I need to transpose a song with full orchestra and singing (say Somwhere Over the Rainbow for example) down to maybe one guitar, and to mimic the right chords as well as the sung melody, your typical chords become diminished, augmented, and whatever have you and it just sounds soooooo much more interesting and beautiful rather then just hearing your C and G chords. And this process can be used on Blues, Rock, whatever you want, once you start integrating ALL the instruments and what their doing, your find that your ordinary chords just don't do the trick anymore, so often when those composer use those obscure chords, it is because they have a melody their trying to get across to the listener
for 3), the answer is most probably theory, theory, theory. If you saw a chord progression in G major that went G C D G B C you'd expect the B to be a Bm, but it quite a common choice to make chord iii a major chord, something the Beatles pioneered. Another common example in bluesier music (Gomez use this a lot) is to use a bIII chord in a major key, so in G major again that would be in a chord progression something like G C D G C Bb B (that is actually a Gomez song). Doing some pretty classical theory, especially four-part harmony voice leading theory, will really help bolster your knowledge of chord progressions. Alternatively look at jazz theory, and chord substitution, such as tritone or common tone substitution, that'll also explain a lot.
Hey for starters right you have to listen to the "right" instrumental music. Have you ever come across the post-rock genre? Full of awesome instrumental music with crescendos and crashes: everything. Good bands to start with are Explosions In The Sky, Mogwai, This Will Destroy You. It is a little hard to get into at first but once you do you will get hooked trust me.

This above paragraph though is just a guide on inspiration and the direction that you should be looking to go to.

Now for tips, personally, i have my own way of making instrumentals. Its a method i call compounding. See what you do is you get a simple recording software like audacity for example. Then record one track with a simple riff like picking of strumming or whatever the sort. You know to form the structure of the song. Now you play this part in a simple rhythm for a short while and stop the recording. Next you record over this track by adding little lead or bass riffs around the same chord structure or along the same scale. And again you just play a short bit(get my drift now??). So you keep on layering on bit by bit until you get something that works and you work around that structure. Its vague i know but hey so is inspiration.

Cheers and good luck mate