Watch the Bluegrass Solo online guitar lesson by Jason Loughlin from Essentials: Country Soloing Styles
Soloing over bluegrass usually embellishes or adds variations to the melody of the tune. Since we're not using a classic bluegrass tune, I'm going to show a few ways I get into the language of this style. One thing I do is try to copy the sound of a fiddle playing legato. I do this by using hammer-ons, pull-offs, and slides. Four note scale patterns that leap up or down a 3rd are very common in bluegrass. Another scale pattern that is used is to do an eighth note run starting on any chord tone. You can connect these together and sustain a long run of ascending and descending eighth notes that always seem to set up a chord change.
A common way to embellish arpeggios in bluegrass is to use a lower neighbor. We can do this for each chord tone and connect them with chord tones. There are common phrases or template licks that set up a chord change. I've nicknamed these licks "tails". You can add endless variations but I'll throw in a couple of standard ones to show you where they're used. Using a secondary IV chord as a substitution works great over the I chord. This helps us impose harmonic movement when we're hanging on a chord. Last, we'll throw in some bluesy licks by using the b5 as a passing tone.