Every KEY has its own "feel".
Em , A , G are commen "funky" keys.
Bm , C, A are commen "blues keys" etc... Bm usually "majestic , sad blues, A more rocking upbeat blues...etc...
There are alot of exceptions but generally speaking....THIS IS GENERALLY the case.
Playing, practicing a variety of styles like say Reggae...youll get a feel of commen keys for that genre.So if you want to compose a reggae track , start plinking around the key of A, B or G or Em ...all commen and often used reggae keys. Practicing , you will draw upon your database of songs you have played before and just remember "if I play an A I can now go to D, E, C from here"......
Practice Practice Practice.
Once you get the feel of the keys (Bm is a commen sad but pretty key), you will hear commen "progressions" of chords that are used to compose songs.When someone says the song is BM , in my head i will automatically know , its going to be very pretty, maybe sad, most likely very melodic and emotional song.
For this it really helps understanding song plagerism cases. One case would be The Eagles "Hotel California" vs Jethro tull "We Used to Know". The main key is BM but based on the melodies, the songwriters didnt really have a whole lot of options on what chords to use to write their songs. So even though the chords are virtually the same , we have two different songs and the chords used are commen for that key (BM) as they are the only chords that fit.
Someone once said any song written in Bm will always be a one of four other songs written in Bm in the history of music. The options of what chords to go to next to sound good is that limiting.
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So YES, while composing a reggae song in A , there are commen "progressions" , sequences of chords that logically go together and will always sound good together, which get people in trouble for plagerism when really from a songwriting perspective , the writer had no other good choices to rearrange how the chords fit together.
So what we learn from all that is practicing unveils that each key has chord structures that generally "fit together well" and will be "logically" the next place the song will go melodically. Sometimes you will have options where to take the song, other times you can only go to one specific chord for the song to "sound good".It depends. But again ...practicing unveils the mysteries of the art.Your goal is to build a database in your head of songs and styles you have played and recall them while working on a new song that is similiar to what you have played before.
Other then that what everyone else said...Think in "patterns".
Also practice playing scales so they DO NOT sound like you are practicing scales.
Skip around scales.
I highly recommend practicing to youtube videos of backing tracks especially a channel called "Elevated Jam tracks".
He has great backings and he puts the scales to use on the screen so you can play along...
In this video he shows you at the start how to apply the scale to the feel of the key of the song then lets you experiment on your own. I think hes the best backing track musician on youtube personally...
Notice also his video song titles. He gives you the key and descibes the "feel". That helps familiarize you with the "feels " of each key and you start learning the similarities and which keys are commenly used for styles of songs.
1:20 into the video he gives you the chords and scales for you to play along with once you get into the groove of the track...
As I stated, this guy s videos are excellent for breaking down styles and song structures and practicing to them you will learn what makes a good reggae song, what makes a good rock song...what makes a good blues song...etc...
At 10:26 he solos using the scale he gave youand you can hear how that scale fits in the context of the chords. He waits for you to discover it for yourself first. These videos are good tools.
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