Different instruments/voices can be specified by adding an instrument letter or instrument number before the tab line.

For example, the Violin playing the 2nd octave "c" note is:
V:2|c    -or-    41:2|c
Instrument Letter
  Instrument Number
  
  Pianos:
P1 Acoustic Grand Piano
 2 Bright Acoustic Piano
 3 Electric Grand Piano
 4 Honky-tonk Piano
 5 Electric Piano 1
 6 Electric Piano 2
 7 Harpsichord
 8 Clavinet
  Chromatic Percussion:
 9  Celesta
 10 Glockenspiel
 11 Music Box
 12 Vibraphone
 13 Marimba
 14 Xylophone
 15 Tubular Bells
 16 Dulcimer
  Organs:
 17  Drawbar Organ
 18  Percussive Organ
 19  Rock Organ
 20  Church Organ
 21  Reed Organ
 22  Accordion
 23  Harmonica
 24  Tango Accordion
  Guitars:
 G 25  Acoustic Guitar (nylon)
 26  Acoustic Guitar (steel)
 27  Electric Guitar (jazz)
 28  Electric Guitar (clean)
 29  Electric Guitar (muted)
 30  Overdriven Guitar
 31  Distortion Guitar
 32  Guitar Harmonics
  Bass:
 B33  Acoustic Bass
  34  Electric Bass (finger)
  35  Electric Bass (pick)
  36  Fretless Bass
  37  Slap Bass 1
  38  Slap Bass 2
  39  Synth Bass 1
  40  Synth Bass 2
  Strings:
 V41  Violin
 42  Viola
 43  Cello
 44  Contrabass
 45  Tremolo Strings
 46  Pizzicato Strings
 H47  Harp
 48  Timpani
  Ensemble:
 S49  String Ensemble 1
  50  String Ensemble 2
  51  Synth Strings 1
  52  Synth Strings 2
  53  Choir Aahs
  54  Voice Oohs
  55  Synth Choir
  56  Orchestra Hit
 Brass:
 T57 Trumpet
 58 Trombone
 59 Tuba
 60 Muted Trumpet
 61 French Horn
 62 Brass Section
 63 Synth Brass 1
 64 Synth Brass 2
  Reeds:
 65 Soprano Sax
 66 Alto Sax
 67 Tenor Sax
 68 Baritone Sax
 69 Oboe
 70 English Horn
 71 Bassoon
 72 Clarinet
 Pipes:
 73 Piccolo
 F74 Flute
 75 Recorder
 76 Pan Flute
 77 Blown Bottle
 78 Shakuhachi
 79 Whistle
 80 Ocarina
 Synth Leads:
 81  Lead 1 (square)
 82  Lead 2 (sawtooth)
 83  Lead 3 (calliope)
 84  Lead 4 (chiff)
 85  Lead 5 (charang)
 86  Lead 6 (voice)
 87  Lead 7 (fifths)
 88  Lead 8 (bass + lead)
  Synth Pads:
 89  Pad 1 (new age)
 90  Pad 2 (warm)
 91  Pad 3 (polysynth)
 92  Pad 4 (choir)
 93  Pad 5 (bowed)
 94  Pad 6 (metallic)
 95  Pad 7 (halo)
 96  Pad 8 (sweep)
 Synth Effects:
  97 FX 1 (rain)
  98 FX 2 (soundtrack)
  99 FX 3 (crystal)
 100 FX 4 (atmosphere)
 101 FX 5 (brightness)
 102 FX 6 (goblins)
 103 FX 7 (echoes)
 104 FX 8 (sci-fi)
  Ethnic:
 105 Sitar
 106 Banjo
 107 Shamisen
 108 Koto
 109 Kalimba
 110 Bagpipe
 111 Fiddle
 112 Shanai
  Percussive:
 113 Tinkle Bell
 114 Agogo
 115 Steel Drums
 116 Woodblock
 117 Taiko Drum
 118 Melodic Tom
 119 Synth Drum
  Sound Effects:
 120 Reverse Cymbal
 121 Guitar Fret Noise
 122 Breath Noise
 123 Seashore
 124 Bird Tweet
 125 Telephone Ring
 126 Helicopter
 127 Applause
 128 Gunshot
 D129 Drum*
* Notes on the drum track
   play these sounds:
Octave|Note
 Name
1|D(#)  High Q (DJ)
1|e  Slap (DJ)
1|f  Scratch High (DJ)
1|F(#)  Scratch Low (DJ)
1|g  Drum Sticks
1|G(#) Square
1|a Metronome 1
1|A(#) Metronome 2
1|b  Bass Drum 2
2|c  Bass Drum 1
2|C(#)  Side Stick/Rimshot
2|d  Snare Drum 1
2|D(#)  Hand Clap
2|e  Snare Drum 2
2|f  Low Tom 2
2|F(#)  Closed Hi-hat
2|g  Low Tom 1
2|G(#)  Pedal Hi-hat
2|a  Mid Tom 2
2|A(#)  Open Hi-hat
2|b  Mid Tom 1
3|c  High Tom 2
3|C(#)  Crash Cymbal 1
3|d  High Tom 1
3|D(#)  Ride Cymbal 1
3|e  Chinese Cymbal
3|f  Ride Bell
3|F(#)  Tambourine
3|g  Splash Cymbal
3|G(#)  Cowbell
3|a  Crash Cymbal 2
3|A(#)  Vibra Slap
3|b  Ride Cymbal 2
4|c  High Bongo
4|C(#)  Low Bongo
4|d  Mute High Conga
4|D(#)  Open High Conga
4|e  Low Conga
4|f  High Timbale
4|F(#)  Low Timbale
4|g  High Agogô
4|G(#)  Low Agogô
4|a  Cabasa
4|A(#)  Maracas
4|b  Short Whistle
5|c  Long Whistle
5|C(#)  Short Güiro
5|d  Long Güiro
5|D(#)  Claves
5|e  High Wood Block
5|f  Low Wood Block
5|F(#)  Mute Cuíca
5|g  Open Cuíca
5|G(#)  Mute Triangle
5|a  Open Triangle
5|A(#)  Shaker
5|b  Jingle Bells
6|c  Bell Tree
6|C(#)  Castanets
6|d  Mute Surdo
6|D(#)  Open Surdo