Today's rock/pop music is a direct descendant of classical music. The similarity to baroque sonatas and concertos is
the clearest - that is why Bach Handel Teleman etc. make the easiest path into classical music to someone familiar with modern rock/pop. Baroque music has the same structure as modern rock/pop - a tune on top of a chord progression. It's a running joke in music circles that Pachelbel's Canon in D sounds familiar the first time you hear it because its chord progression appears in countless modern pop tunes. The basic baroque ensemble is like an unamplified rock band without drums. There is a rhythm section called the "continuo"
constisting of a bass instrument like a cello or viola da gamba or bassoon - that's like the bass guitar - and a chordal instrument like a harpsichord or organ or lute or
theorbo or ... that's like the rhythm guitar or piano or organ. Then there is a violin and/or flute or other melody instruments - that's like the lead guitar and/or saxophone or singer. The continuo part was
usually written in a notation called 'figured bass' that was
analogous to modern chord charts. Besides that, the soulful singer songwriter goes back at least to the medieval troubadours, but appears in essentially modern form with the lute song composers of the 16th and 17th century - the model here is John Dowland, who in addition to composing a lot of
melancholy songs, also composed some guitar-god-like solo instrumentals. And, this lute music was typically published
in a tabular notation a lot like modern guitar tab.
Not to downplay the influence that the classical music tradition has had on popular music, I think it's incorrect to say that rock and pop are direct descendants of classical music. Rock music, for example, is very clearly directly descended from folk music traditions.
