The Senate's continuing war of nerves over a pre-election vote on the tax-cut bill intensified yesterday as the respective sides took to new harrassment tactics to force -- or delay -- a vote on the measure.

In a preshowdown skirmish, the Senate Finance Committee overwhelmingly approved a "sense of Congress" resolution calling for both houses to schedule floor votes on the tax-cut bill before the October recess.

Meanwhile, liberal senators -- hoping to mire the tax bill in extraneous riders if Republicans succeed in tacking it onto minor tax legislation before the coming recess -- introduced a spate of narrow-interest amendments.

The outcome of the skirmish remained very much in doubt late yesterday, with indications that the Republicans may not even get an opportunity to attach the tax-cut bill to other legislation until some time late next week.

Sources reported that Senate Majority Leader Robert C. Byrd (D-W.Va.) has decided to postpone any floor action on even the minor tax bills now on the docket until just before the senators go home -- currently scheduled for Oct. 2.

Democratic sources said they expect the Republicans will not have a chance to try their add-on tactics until the Senate takes up its continuing appropriations bill -- possibly the final item on the chamber's agenda.

The hope by Democratic leaders is that the ploy would ease pressure to support a tax reduction. President Carter has called on Congress to shun any pre-election tax cut, on grounds that the measure would be inflationary.

The developments came as, separately, the Finance Committee voted to extend several existing provisions in the tax code -- including one dealing with the tax treatment of so-called "independent contractors," such as some salesmen and real estate agents.

For more than a year now, the two houses have been wrangling over a proposal by the administration to treat these workers as employees of their companies -- rather than as self-employed, their current status -- which would force employers to pay Social Security and unemployment taxes for them. A previous law putting off any change in their status expires in December.

The Finance Committee voted yesterday to extend the current law through all of 1981 and to renew other existing legislation dealing with write-offs for restoration of low-income housing and a taxicab fuel-tax exemption.

The panel put off a vote on a compromise bill designed to simplify the tax treatment of capital gains on installment sales of real estate and other property, after a flap over a provision affecting enforcement in tax-evasion cases.

Committee Chairman Russell B. Long (D-La.) rescheduled action for the panel's next meeting after Sen. Harry Byrd (Ind-Va.) invoked a parliamentary rule to delay final action. Long called the measure a significant "reform."

The effort to try to sidetrack any tax-cut bill by attaching special-interest amendments is being mounted by Sens. Edward M. Kennedy (D-Mass.), Dale Bumpers (D-Ark.) and Howard M. Metzenbaum (D-Ohio).