The standard-bass-accordion suffers (especially in Germany, Austria and Switzerland) still under the prejudice that's an instrument for bad popular music, but many different kinds of music can be played on this instrument. This possibilities are described below. Unfortunately common bass accompaniement can't be used mostly. Often only key-note-basses and third-basses are used or new chords are build with one or two chord-basses (and mostly one key-note-bass or one third-bass).
Some examples (all can be played without the diminished-chord-basses):

Upper table could be enlarged with more extreme chords. Some chord can be interpreted as other chords too, e.g. C⁶ = Am⁷ or Cm⁷ = E♭⁶. Doubling of third (chord C played with E+c or chord Cm played with E♭+cm) isn't desired in a few situations. Doubling of third or seventh often sounds ugly in seventh chords. This is especially valid if fifth is absent. It's hard to finger some chords. Therefore they aren't suitable for a quick playing. These chords really show to advantage in a slower playing. If you prefer notation with B = H & B♭ = B, have a look at german version of table.

Key-note-basses and third-basses result in a chromatic scale with a range of a major seventh, normally from C-B, on instruments with 40 or 48 basses. To play on key-note-basses and third-basses comfortably an instrument with 60 or 72 basses is required.

Download a bass-table for standard-bass-accordions for a better orientation:

If bass-registers are available scale range can be extended round about an octave. Then scale range includes C–b⁰. It can't be always avoided that some tones tilt into their octave above or below in bass part. That results in limited scale range (without bass-registers C–B). This effect interrupts especially a cantus firmus in bass-part! To reduce this effect to a minimum tune should be transposed. Transposition isn't critical because standard-bass-accordion is tuned up to equal temperament.

Download here an arrangement of an organ tune composed by Karlmann Kolb (1703-1765) as MIDI-file and picture (PNG):
Proposal for registration:
treble: 8′ or 8′+4′; bass: sounds in great octave, as piano as possible

Comment: A transposition was required because range of scale of key-note-basses and third-basses includes only C–B. 5th note in bass part would tilt into lower octave in original scale. This can't accept here because bass part introduces subject (dux) of fugue. Bass part is signed as well with symbols that are normally used for accordion to explain use of key-note-basses and third-basses.

To vary playing gracefully treble should contain at least three ranks at 16′+8′+8° =. This enables already 5 useful registrations:

= 8′        = 8′+8°        = 16′        = 16′+8′        = 16′+8′+8°

Instruments with four ranks are mostly flexible with ranks at 16′+8′+8°+4′ =. Instruments with ranks at 16′+8′+8°+8O = can be used only for some special kinds of music. They are build only some time today.
A fifth rank is only useful at 2⅔′, but instruments with a fifth rank at 8O are build more often. Such instruments are rare, weighty and expensive and they've as well a convertible bass. This can be switched between standard-bass and a single-tone-bass.
Keyboard range of treble should include g⁰–c³ on accordions which have a treble with a piano-like keyboard. Scale range can be extended round about an octave below if registers are changes during playing. Keyboard range of treble is normally greater on instruments which have a treble with a button keyboard and 40 or more basses.
Tunes with two or three parts can be mostly played without any problems on standard-bass-accordion but it should be avoided to play two parts with key-note-basses and third-basses because this results in a terrible grumble mostly. This is only useful in a few exceptions, e.g. some medieval tunes whose two lowest parts only contain long notes those sound together in fourths and fifths, or first or final chord should be forced with a fifth¹ to key-note in bass part. Tunes with four parts can cause problems because three parts must be played on treble. Some parts of tenor part must be played one octave higher especially on instruments which have a treble with a piano-like keyboard. Instruments which have a treble with a button keyboard cause less problems because these keys (buttons) are placed more together. If tenor part hasn't any solo function result is mostly acceptable. Breakpoints should be placed by this part transfer so that no large intervals result from this. An interval of a fifth should not be exceeded.

¹ATTENTION PLEASE! Upper fifth can be only played to key-notes C–E. Only lower fourth can be played to key-notes F–B!

Bass of a standard-bass-accordion contains normally following basses:

Key-note-basses and third-basses: one rank, scale range C–B + one rank, scale range c⁰–b⁰
Chord-basses: One rank, scale range c¹–b¹ + one rank, scale range c²–b² (is absent some time)

Equal temperament of standard-bass-accordion causes that all scales sound equally. Because chords are only created out of a range of a major seventh they sound in different inversions. Following results from scale range described above e.g. for major- and minor-chords (triads):
[Chords are signed with symbols that are normally used for accordion!]
c, cm, c♯, c♯m, d♭, d♭m, d, dm, d♯, d♯m, e♭, e♭m, e, em sound as fundamental chords (structure: key-note, third, fifth)
f, fm, f♯, f♯m, g♭, g♭m, g, gm, g♯m, a♭m sound in their 2nd inversion (structure: fifth, key-note, third)
g♯, a♭, a, am, a♯, a♯m, b♭, b♭m, b, bm sound in their 1st inversion (structure: third, fifth, key-note)
Situation becomes more complexity by seventh-chords (tetrads) because three inversions exist for fundamental chord. Moreover these chords are only realized as triads in some instruments whereby fifth is absent.
Opinions differ about usefulness of diminished-chords. Nevertheless they are absent (look into bass-table) in many instruments. If equal temperament is used only three different diminished chords (tetrads, minor thirds are stacked one over another) exist. Fundamental diminished chords have keynotes C (chord: c, e♭, f♯, a), C♯ (chord: c♯, e, g, b♭) respectively D♭ (note d♭ instead of c♯) and D (chord: d, f, a♭, b). All other diminished chords are only inversions of these three chords.
If tune is especially accompied with major- and minor-chords tune can be presented with a timbre by use of different inversions of chords (fundamental chord, 1st inversion, 2nd inversion) because different inversions of chords represent different timbres. Tune must be transposed at times into suitable scale but that's not a problem because standard-bass-accordion is normally tuned up to equal temperament.

Unfortunately it's usual to couple ranks for chord-basses onto ranks for key-note-basses and third-basses. Through that four octaves sound on each key-note-bass or third-bass. This causes a very thick and ambiguous tone that sounds mostly too loud as against treble. If bass can be registered at least two ranks sound as well. To remove this nuisance it's required to modify bass mechanism of instrument. Bars must be severed which couple key-note-basses and third-basses onto ranks for chord-basses. Bar-segments can often be removed in modern instruments reversibly. If connection however is manufactured rigidly side nippers will help only. This method is destructive and therefore mostly irreversible. You must decide in this case but it's worth while! The remuneration is a key-note based, plain and clear bass sound :-)    Folk tunes sound with their typical bass accompaniment very well too. If you don't comprehend bass mechanism you should comission an accordion-maker with this task.

If you have an instrument with a convertible bass or an additional single-tone-bass you don't need to do any things those are described above. Unfortunately these instruments cost a lot of money and therefore they are used considerable rarely than standard-bass-accordions.