Interval training is the key here. You should be able to figure out how distant the notes are, ascending or descending. The best way, as it has worked for me at least, is take a song and try playing on your instrument of choice. Take easier parts of the song for starting out. In many cases you can't directly figure out the flow of the song and that's where instrumental versions of the song can help you. Following clean instrumental tones is very much helpful. In addition pay keen attention while listening to the tune.
Of course there are other mainstream methods and softwares, mobile apps which play an interval and you go about and guess it until you really learn. https://play.google.com/store/apps/details?id=com.kaizen9.fet.android&hl=en
But I will strongly emphasize on avoiding such tools and really try and play songs and melodies, you can record yourself and hear for feedback or play to your friends even.
I always recommend this app I made to help me study how notes relate on the fretboard. It has a lot of theory stuff, like modes and interval types, just built in
https://play.google.com/store/apps/details?id=org.wormclaw.fretfulfree
Just bought "The Practical Guide to Modern Music Theory for Guitarists: The complete guide to music theory from a guitarist's point of view (Guitar theory)." Supposedly, it's just like everything else out there, but the author does a good job at explaining it simply (cuz mah brain always fried).
https://www.amazon.com/gp/product/1911267779/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&psc=1
Here are a couple good (and free!) apps that I started using in the last month or so.
This one, just called "music sight reading". It doesn't cover notes above or below the staffs, or sharps and flats, but it gets the basics of what notes are what.
This one, "rhythm trainer" does just the rhythm patterns. Rhythms are one of the most challenging parts of reading for me. I haven't used it as much as the other one but it looks good so far.
This book is the best chord progression source I've ever found. There's another good website with an app that is tremendous for both chord progressions, and lead melodies, but I can't for the life of me remember what it is. It was color coded and everything.
Not necessarily guitar specific, but http://chordify.net is really handy when tabbing new songs. It'll automatically assign chords on beat to a YouTube video. They're sometimes a bit wrong, especially if there's vocals over the measure, but it's an excellent starting point.
Want to know those weird chords in Justin Beiber's "Yummy"? https://chordify.net/chords/justin-bieber-yummy-lyrics-unique-vibes
Boom, Gm9 Am7. Tab done.
buy these, and listen to the author's podcasts:
https://www.amazon.com/gp/product/B074C51QK7?ref_=dbs_dp_rwt_sb_tkin&binding=kindle_edition
i don't mean to diminish your adhd, but i don't think that's your problem. the core issue and the reason why theory isn't something most guitarists pursue is because it's complex, and as you've noted, very, very deep. it's easily as technical as many engineering fields, sometimes more so. thorough understanding requires hours and hours of work, study, and repetition. so while you may struggle more than the average person due to your adhd, keep in mind that your experience is likely not unique, and something most people battle in some regard.
I thought Lee Nichols’ book had the best simple explanations I’ve seen. Get the paperback instead of Kindle so you can make notes on the pages and diagrams.
https://www.amazon.com/dp/1093508302/ref=cm_sw_em_r_mt_dp_Pmr-Fb3MWQTPH
I'd suggest getting one of those guitar chord posters (or just printing out a .pdf). It's nice to just be able to glance over at it for reference without having to pause to look something up on a computer or your phone.
Something like this would do for a beginner:
https://www.amazon.com/Reference-Learning-Best-Music-Stuff/dp/B078S136R7
"Best" is pretty subjective. What's your current skill set? What do you want to learn to do?
The Noad Book is super easy and lays a great foundation but it's not what everyone is looking for.
Yep! I'm very proud of it. Still working on the last part, intervals and chords. You're very welcome. If you find it useful, please leave review on the rosetta pattern at amazon, https://www.amazon.com/dp/1794677976. Thanks!
Check out the dunlop reverend willy strings, they are somehow associated with Billy Gibbons and they are like rubber bands. They are personally a little too light for my taste but I don't think you can snap them without a knife https://www.amazon.com/Dunlop-RWN0738-Reverend-Electric-Strings/dp/B003B1OTCK/ref=sr_1_1?crid=Q27QBZBZ1Z48&dchild=1&keywords=billy+gibbons+guitar+strings&qid=1603571999&sprefix=billy+gibb%2Caps%2C194&sr=8-1 edit. ling
Hard to tell but it certainly sounds like the key of A Aeolian or A minor. I wrote an app for this that might help you. It's 💯 free: https://play.google.com/store/apps/details?id=com.shanahan.circleoffifths
Also available on iTunes as "Simple circle of fifths"
I love the Complete Music Reading Trainer app. Just a few minutes a day for a few days has helped me to instantly recognize each note on the staff, as well as several notes above and below it.
The first part of the app is free and then to unlock everything is about $3, I think. Definitely worth it!
It's fun, too, almost like a game.
https://play.google.com/store/apps/details?id=com.binaryguilt.completemusicreadingtrainer
Shameless plug; I wrote an app that helps with this. It's free and no ads. It's on the App store and Play store. Here's a direct link if the mods are cool with it.
https://play.google.com/store/apps/details?id=com.shanahan.circleoffifths
Also Harmony and Voice Leading is a good resource. starts from the ground up. You can usually find PDF copies online of the older versions. (Here is the 3rd edition)
Fundamentally harmony is nothing without a melody. So understanding how to write melodies comes first. Even if you just write chord progressions there is an implied melody. It's why progressions that use inversions to rearrange the movement of the voices(notes) in a chord, sound better. They have voice movement that implies a stronger melody.
If you aren't interested in classical music at all then really getting into fundamentals of harmony can be boring but I really suggest just looking at music history and understanding how music progressed to where it is at today. Classical composers really set the foundation for a lot of the tricks we use today. Then you get to the era of impressionist artists and people like Debussy push the functional harmony to the side and find ways to accomplish the same thing without it.
I want to give you material for the guitar since this is a guitar oriented space but really its hard to learn about this stuff with just a single instrument. Its more of a conceptual thing that you learn then figure out how to apply to your instrument.
Basic knowledge for this is knowing your intervals on the guitar, then major/minor scales which leads to learning triads, and then inversions. Then learning diatonic harmony (also called functional harmony some places).
If any of this brings up any questions feel free to ask. I can help you figure things out or lead you to some specific info.
Look into latin guitar grooves. MI Press has a great straightforward book on the subject, here is an amazon link: https://www.amazon.com/Latin-Guitar-Essential-Brazilian-Afro-Cuban/dp/0634006037/ref=sr_1_fkmr0_1?ie=UTF8&qid=1475267839&sr=8-1-fkmr0&keywords=mi+press+latin+guitar
This is basically 'This Love' with a Bossa Nova-ish groove. There are guitar fingerstyle patterns that mimic the arrangement of a guitar & bass in an ensemble context, by putting the patterns the bass would play on the 6th and 5th string of the guitar and putting chord tones on the higher 4 strings. The MI book gets started with this stuff. Most stuff you can play with hybrid picking (pick and fingers) or all fingers.
Hope that helps, good luck.