instruments in pop music
As we know, most kinds of music are made with different instruments layered together. In pop music there are some instruments that are commonly used, whose function we are about to describe. Every instrument has its own extension and frequency range, and once blended together their sound covers almost the whole audible frequency spectrum. Part of the job of a mixing engineer is to make sure that frequencies are evenly distributed, and that each instrument has its own space and does not conflict with other sounds.
Of course the following list is not comprehensive, but it covers the instruments that we are most likely to find in pop music. Different genres may have their own particular instruments, but once you are familiar with the principles described below, it should not be difficult to find out what their role and frequency range is. The purpose of these class is not to be a guide for mixing or eq-ing, but it aims to make you become able to recognise what instruments are playing in a song.
The rhythmic section has the purpose to set the groove and the tempo at which the song is played. Often it is limited in melodic contents, but very rich in dynamics and accents that are the basis which the other instruments play on. The following instruments are commonly used for this purpose:
Drums are the best known tempo-keeping instrument ever, but their capabilities are not limited to being some sort of metronome: a drumkit is made of different pieces which all sound differently, and a good drummer is able to keep the tempo whilst conveying a sense of groove that is consistent through the song by hitting the different pieces with different strength. The 'human factor' of a drummer, which is the fact that there are extremely small variations in the tempo (a drummer is not a computer...), is actually what most conveys the sense of rhythm and groove, especially when listened to together with other instruments. It is so important that computer based drum machines, which could be 100% perfectly on time, try to recreate this imprecision! These are the part of a standard drumkit:
Kick drum: the largest drum, often occurs in strong accent. It has the lowest frequency range, with the 'body' ranging from 60Hz to 120Hz and the resonance in the region of 120Hz up to 800Hz. There is also a component between 2500Hz and 4000Hz that contribute to the attack of the sound (the snap). Sometimes the snap reach higher frequencies too, but there is very little beyond 7000Hz.
Snare: the snare is usually employed in weak accents, and has a bright and full sound, also thanks to a metallic chain tightened at the bottom of the drum that vibrates when the drum is hit. The body of the snare is also in the low region, but not as low as the kick drum, let's say in the range of 150Hz to 200Hz. The chain adds middle range frequencies in the range of 2500Hz to 4000Hz, and there are some elements of 'air' in the high end. Very often snare drums resonate at a very precise frequency that could be between 600Hz and 1500Hz (the bell), this ringing can be attenuated if unwanted. The kick drum and snare are usually alternated.
Hihat: often hit in quarter, eighth or sixteenth regular intervals, it adds a high end to the kick and snare pattern. There is very little low frequencies in most cymbals, and much more in the mid and high regions. Most content between 2000Hz and 5000Hz, and air and brightness at around 12KHz.
Toms: toms are used to vary the drum pattern, adding sounds of different pitches. There are two rack toms and one floor toms in a standard drum kit. Depending on their size, the main component is in the low range, between 150Hz and 800Hz. The impact of the stick with the skin is, for all drums, in a higher range, between 2000Hz and 4000Hz.
Overhead cymbals: also called just 'overheads'. Like the hihat, most of their contents is in the hi mid range and in the high end. There are two types of cymbals in a standard kit, crash cymbals and ride cymbals. The first type is often used to highlight a strong accent, or to add some brightness in some passages. The ride cymbal is often used similarly to the hihat.
Drum loops: electronic drums are often added on top of acoustic drums. Their frequency range may vary, have a listen to a few of them. Sometimes they are also used instead of an acoustic kit, however it usually quite clear if the drums are electronic or acoustic.
Bass lines combine the rhythmic strength of a percussive instrument with the melodic content of a string instrument. Whether performed by an bass guitar or a synth, they add low end to the songs and work together with the drums (especially the kick drum) to create the groove.
Bass guitar: the main body of the bass guitar is in the low range, mostly between 80Hz and 800Hz. Higher notes reach the mid range frequencies, and different playing styles can add different overtones and harmonics: playing with a plectrum or slapping adds frequencies in the hi mid and high area.
Synths: electronic sounds are more and more common in pop music nowadays, and they find particularly successful applications in bass sounds. Being synthesised sounds, there are virtually no limits to the frequency range that they can cover.
Part of this category are all the instruments whose parts contribute to the melodic and harmonic development of a song. Of course this does not means that they cannot be part of the rhythmic section: in facts many instruments can be part of both categories, depending on how they are played. It is often the case of guitars, which can be highly rhythmic or highly melodic.
Acoustic guitar: acoustic guitars can have nylon strings or, more commonly, steel strings. Nylon strings have a softer and rounder sound, while steel strings are sharper and brighter. Much of the content of acoustic guitars is in the mid and hi mid range, but they have some 'air' in the high end. They are tuned an octave above bass guitars. Acoustic guitars are very effective as rhythmic instruments as well as melodic:
Electric guitar: widely used across different genres, electric guitars can be used clean or with different degrees of distortion. Both styles can be employed as a support to the rhythmic section or as lead instruments with very good results. The frequency range is similar to acoustic guitars, but effect such distortion may change it. Most contents in the mid and hi mid range, though.
Piano, organs, and synths: this category includes basically all keyboard instruments. All of them lend themselves very well to be used as rhythmic or lead instruments. Depending on the music genre instruments with long sustain like organs or synths can be used to create a pad: a sort of harmonic base on which other instruments can develop their melodies. Pads are usually made of long and sustained chords, but that can vary. The frequency range of such instruments is usually very wide, from low bottom ends (say in a the 100Hz area) to frequencies near to 6KHz or more.
Lead vocals: lead vocals develop the main melody of the song and can convey emotions through words as well. There is usually one lead vocal line at a time, but sometimes there can be more (duets or trios, etc.). The fundamentals of human voice may range between 100Hz and 1300Hz, but in the mid range 2000Hz - 4000Hz there very important components in regard to the intelligibility. To the higher end belong some consonants and the sibilants, that can reach 7,5Khz and more.
Backing vocals: these vocal lines are used to enhance certain passages of the led vocals, or to embellish particular parts of the song that in which the voice needs to be thicker and wider. Many times the backing vocals are actually sung by lead singers in overdubbing sessions, so they basically do the backing vocals for themselves. In other cases backing vocals are sung by different singers. There may be different layers of backing vocals, from one to generally not more than 3-4.
As we said, there are many other instruments that we cannot cover in this course, but if you can recognise the instruments that are part of a song, it will certainly be useful to understand the mixing procedures that took place. There are many tests that you can do to practice in the tests section, but you can also try to recognise the instruments in your favourite records, it is a very good exercise.