That's almost as hard a question as asking "20th century music, where do I start?", since there many sub genres and styles, some as far apart as Philip Glass and Skillrex are today.

There are two broad schools, French and Italian, with German and English composers also providing important pieces. Spanish music was also a huge thing but I'm only beginning to get into it.

Italian, the original, Where the Florentine Camerata (a group of musicians, artists, and scientists associated with the early scientific revolution) attempted (badly) to revive Greek musical and dramatic forms, accidentally creating modern Tonality and the art form of Opera. To do this they stripped out the complex polyphony of the 1500s, adopting simple, improvised harmonies below a dominant melodic line that attempted to mimic natural speech rhythms. Operatic recitative, Spoken word, and even modern rap have some of their heritage in them.

They focused mostly on secular vocal music, with a side order of lute song and dance music. Towards the middle of the century the Castrati becomes the primary heroic/romantic voice type, since Italy banned women from singing in opera (and often church)

Key composers are Monteverdi (One famous paper on music 1600-1650 is called "The development of Opera from Monteverdi to Monteverdi"), The Caccini Family (Francesco and his daughter, Francesca), and the lute song of Vincenzo Galilei (father of that Galilei). Later, Cavalli is important in transitioning opera towards the florid vocalism and melody of the early 18th century arias.

Here's a performance of L'Orfeo, composed in 1607, the first great opera (though the genre had been around for a decade)

And here's an album of Francesca Caccini's songs

And here is Vincenzo Galilei's chill lute beats

And for the end of the century Corelli's variations on La Follia (Compare if you're familiar to Handel's famous Sarabande of 50 years later.)

French style came a bit later. Focuses a lot more on instrumental, dance (This is where ballet begins, and where court dance reaches its artistic peak), and church music, though French opera is also very important and develops the older method of operatic singing in a lyrical direction, lengthening the passages but never really falling into arias proper and having far more duets and ensembles. The music is generally a bit easier on the ears to modern listeners, and has a lot of spectacle and flair, suitable for the court of Louis XIV.

Two primary composers, Charpentier, and Lully.

Here is Te Deum by Charpentier which you'll likely have heard before

Here is a Pascalle (a type of early court dance) from Lully's Ballet Armide

England was in a musical decline in the first half of the century due to an excess of Protestantism, But made up for it with great popular and radical music.

In the second half we get the glory of the Restoration Semi-Opera, a play, often modified Shakespeare, with extended musical interludes. And of course, Purcell who in 35 years of life rivalled Mozart in brilliance.

Dido's Lament, by Purcell

When Cannons are roaring, a popular roundhead song

Unfortunately the Royalists got better composers

And some country dances based on folk tunes of the era

In Germany we mostly see great developments in Organ Music , most German composers being copiers of the Italian styles. This allowed Bach to exist though so we can't criticise too much

Finally, Spain and her colonial possessions were somewhat isolated, but influences from the Americas and remaining Islamic styles were combining to produce what we begin to think of as the distinct sound of Hispanic musical styles. Guitar music, of course, was a major subgenre. I'm currently trying to learn more.

Compare this Spanish Variation on La Follia with the Italian one I posted above to compare styles.

There's so so much more, I haven't even talked about central European, Balkan, Russian, or Mediterranian music. Let alone non-European styles and the many hybrid styles European imperialism was producing as oppressed peoples co-opted instruments and theory and applied them to their own musical traditions.