How often are you thinking about your arrangement when writing a new song? It isn't always about what instruments are playing. A lot oaf arranging has to do with what the instruments are playing...
Rhythmic vs. chordal support
When most of us hear the word rhythm, we immediately think of percussion. Drums, shakers, tambourines, etc. But many other instruments provide necessary rhythm to a musical track. Let's take a look at funk music for instance; "Good Times" by Chic has a killer guitar line that instantly sets the groove of the song. In The Knocks "Classic", the rhythmic guitar helps drive home the stomp clap groove from the drums.
Rhythmic bass lines is something we are all accustomed to as well. From "Billie Jean" by Michael Jackson or "Money" by Pink Floyd, the bass guitar licks instantly gets us in the groove of the song. While these instruments can usually be considered melodic instruments, providing the key or chords of the song, they can play both roles quite easily.
On the other side, we have chordal support and pad instruments. These can lay down the foundation of the key, chords, and tonality of music. "It's Probably Me" by Sting has luscious chords, providing a "swimming" feeling in the intro. This can place the listener in a space, while providing a theme for the song. While there is plenty of rhythmic aspects, these support instruments give a refrain from the ever moving guitar drums. In "Ode" by LAIK, the symphonic strings and piano add a mournful, sorrowful feel, while the small rhythmic parts lift up the song in the chorus.
Balancing these two can help you create hooks and interesting counterpoints in your music.
When combining multiple instruments, timbre plays an important role. Many instruments share similar timbre spaces, which can create "masking" or the inability to differentiate each part. For example, having two guitars playing in the same timbre, yet playing different parts can be difficult to hear. If one guitar is playing an open G chord, while the other is playing an open G arpeggio, the arpeggiated part might not come through as much. However, if the arpeggio guitar were to play one octave higher, this could open up space for both instruments to be heard equally.
This is a common mistake when blending multiple instruments like guitar, piano, synths, voice, etc. Try to create a space sonically for each instrument, instead of trying to crowd them all together in the same timbre. Let the piano play higher octaves, the synths lower, and let the guitars split up. This way everything has its own space. Sometimes even taking some instruments out can help "free up" some sonic space for a more important part to be heard.
Utilizing these ideas can help you create a better balance in your next piece. Give them a try and see if it helps your arrangements come to life...