Here is a list of abbreviations I use for instruments. Most of them are directly from Rust's discography. Any I didn't find there, I made up myself.
a Arranger acc Accompanied acg Acoustic Guitar ah Alto Horn as Alto Sax b Bass bar Baritone Sax bb Brass Bass (tuba) bcl Bass Clarinet bd Bass Drum bh Baritone Horn bj Banjo bkv Vocals bo Bongos br Brass bsn Bassoon bsx Bass Sax bt Bass Trombone c Cornet ca Cor Anglais (Eng. horn) cel Celeste cl Clarinet Cm C-Melody Sax cng Congas con Conductor d Drums db Doubling dir Director elg Electric Guitar elo Electric Organ elp Electric Piano eu Euphonium f Flute fh Flugel-Horn frh French Horn g Guitar gfs Goofus/Cuesnophone h Harmonica har Harmonium hfp Hot Fountain Pen hrp Harp k Kazoo key Keyboards ldr Leader md Mandolin mel Mellophone o Oboe oc Ocarina or Organ (pipe) oth Other p Piano pac Accordion per Percussion pic Piccolo qv quo vides r Reeds sax Sax sb String Bass sd Snare Drum snt Synthesizer ss Soprano Sax stg Steel Guitar str Strings sw Slide Whistle syn Synclavier t Trumpet tam Tamborine tb Trombone th Tenor Horn tim Timbales ts Tenor Sax tym Tympani u Ukelele unk unknown v Vocalist vbh Vibraharp vc Violoncello vib Vibraphone vl Viola vn Violin vtb Valve Trombone w Whistling wb Washboard x Xylophone