Questions about scales

Scales by themselves won't sound cool - it's what you do with them that matters... and you can use any scale to make a cool solo. The most common scales will be the pentatonics and the blues scale for rock soloing, followed by the major and harmonic minor scales.

In any scale, you'll have a few tones that sound really, really solid against the chord, one or two others that sound weaker but still ok, and the remaining two or three that don't sound terrible, but they don't sound great (I'm talking about one note held over the chord here). They're all important in building solos.

A solo is constructed of phrases. They can be bits of scale runs, parts of arpeggios, leaps from one note to another, or all of the above. You want to know where the strong notes are, because that's where you want to be at the chord change - if you're in C, and the chord is changing from C to F, you want to land on a note that's in the F chord (F, A, or C). The F will sound the most solid, and that's often used to end a solo - land on the root note of the final chord, and everything before that point sounds a little more intentional.

For the chord changes before that last chord, roots are ok - but you don't really want to hit a root at every chord change... it gets boring having all these 'final' sounds in a solo. Fifths are great for those in-between chords... so for the C-F change, you'd want to hit the C note at the chord change, and keep going from there.

I'd tackle it in this order, and you'll see a noticeable improvement in the way you sound.

1. Learn the scale you want to use next
2. Figure out the chords used in the rhythm track
3. Learn the note spellings of those chords (you can learn the spellings of major, minor, and seventh
chords by rote - you're only talking about 36 different chords - and it'll pay off for everything you play)
4. Figure out where those chord tones fall in the scale - especially the roots and fifths. For a progression in
C, with C-F-G7 chords, you're only locating notes C, D, F, and G.
5. Play around with your improvising, landing on G or C for C chords, C or F for F chords, and D or G for
G7 chords.

The next step is a tough one... you want to play the notes you mean to play. We all start improvising in a pretty random fashion, hitting notes from the scale or scales we've learned. That ends up with random solos... sometimes they'll sound great, sometimes they'll suck. To get beyond that, you need to make the connection between head/ears/fingers. Think of a melody, and play it. It'll probably be different from what you heard in your mind. Figure out where you went wrong, and fix it. Repeat with a different melody. (This stage takes some time - keep working at it!)

You want to reach the point where the phrases you play are the ones you meant to play - at that point, you're not doing random notes, but communicating your musical idea. At that point, you're really improvising - and it's quite a rush!

The final step takes a lifetime... listening to what others do, copping their great ideas and making them your own, stretching your ears to new sounds and making your fingers follow, finding your own voice, and honing it.

Jazz author Hal Crook gives guidelines for the stages of melodic improvising that players go through...

Beginner - developing accuracy in expressing your musical ideas (the first 4-6 years)
Intermediate - developing 'musicality' in those ideas (the next 4-8 years)
Advanced - having those ideas be both musical and creative in the way they build a solo (the next 6-8 years)
Master - being consistently musical, creative, and original - another 12 or more years, for 30+ years total.